Add more entity passivation strategy traces and simulations (#30994)

* Add optimal clairvoyant algorithm to passivation strategy simulations

* Add natural zipfian distribution trace using text of Moby Dick

* Add some looping access pattern traces from the LIRS paper

* Add CloudPhysics access pattern trace from LIRS2 paper

* Add Wikipedia access pattern trace to passivation simulations

akka-cluster-sharding/src/test/resources/arc-trace-database.conf

@@ -11,6 +11,14 @@
 #   ╔══════════╤═════════╤════════════╤═════════════╤══════════════╗
 #   ║      Run │  Active │   Accesses │ Activations │ Passivations ║
 #   ╠══════════╪═════════╪════════════╪═════════════╪══════════════╣
+#   ║   OPT 1M │ 20.19 % │ 43,704,979 │  34,879,633 │   33,879,633 ║
+#   ╟──────────┼─────────┼────────────┼─────────────┼──────────────╢
+#   ║   OPT 2M │ 31.79 % │ 43,704,979 │  29,810,905 │   27,810,905 ║
+#   ╟──────────┼─────────┼────────────┼─────────────┼──────────────╢
+#   ║   OPT 4M │ 48.09 % │ 43,704,979 │  22,685,636 │   18,685,636 ║
+#   ╟──────────┼─────────┼────────────┼─────────────┼──────────────╢
+#   ║   OPT 8M │ 74.93 % │ 43,704,979 │  10,957,661 │    2,957,661 ║
+#   ╠══════════╪═════════╪════════════╪═════════════╪══════════════╣
 #   ║   LRU 1M │  3.09 % │ 43,704,979 │  42,356,500 │   41,356,500 ║
 #   ╟──────────┼─────────┼────────────┼─────────────┼──────────────╢
 #   ║   LRU 2M │ 10.75 % │ 43,704,979 │  39,007,141 │   37,007,141 ║
@@ -67,6 +75,34 @@ arc-traces=${?ARC_TRACES}
 akka.cluster.sharding {
   passivation.simulator {
     runs = [
+      {
+       name = "OPT 1M"
+       shards = 100
+       regions = 10
+       pattern = arc-database
+       strategy = optimal-100k
+      },
+      {
+        name = "OPT 2M"
+        shards = 100
+        regions = 10
+        pattern = arc-database
+        strategy = optimal-200k
+      },
+      {
+        name = "OPT 4M"
+        shards = 100
+        regions = 10
+        pattern = arc-database
+        strategy = optimal-400k
+      },
+      {
+        name = "OPT 8M"
+        shards = 100
+        regions = 10
+        pattern = arc-database
+        strategy = optimal-800k
+      },
       {
         name = "LRU 1M"
         shards = 100
@@ -247,6 +283,34 @@ akka.cluster.sharding {
       }
     }
 
+    optimal-100k {
+      strategy = optimal
+      optimal {
+        per-region-limit = 100000
+      }
+    }
+
+    optimal-200k {
+      strategy = optimal
+      optimal {
+        per-region-limit = 200000
+      }
+    }
+
+    optimal-400k {
+      strategy = optimal
+      optimal {
+        per-region-limit = 400000
+      }
+    }
+
+    optimal-800k {
+      strategy = optimal
+      optimal {
+        per-region-limit = 800000
+      }
+    }
+
     lru-100k {
       strategy = least-recently-used
       least-recently-used {

akka-cluster-sharding/src/test/resources/arc-trace-search.conf

@@ -11,6 +11,12 @@
 #   ╔════════════╤═════════╤════════════╤═════════════╤══════════════╗
 #   ║        Run │  Active │   Accesses │ Activations │ Passivations ║
 #   ╠════════════╪═════════╪════════════╪═════════════╪══════════════╣
+#   ║   OPT 250k │ 30.13 % │ 37,656,092 │  26,309,294 │   26,059,294 ║
+#   ╟────────────┼─────────┼────────────┼─────────────┼──────────────╢
+#   ║   OPT 500k │ 45.95 % │ 37,656,092 │  20,354,161 │   19,854,161 ║
+#   ╟────────────┼─────────┼────────────┼─────────────┼──────────────╢
+#   ║     OPT 1M │ 65.55 % │ 37,656,092 │  12,970,868 │   11,970,868 ║
+#   ╠════════════╪═════════╪════════════╪═════════════╪══════════════╣
 #   ║   LRU 250k │  3.07 % │ 37,656,092 │  36,498,516 │   36,248,516 ║
 #   ╟────────────┼─────────┼────────────┼─────────────┼──────────────╢
 #   ║   LRU 500k │  7.53 % │ 37,656,092 │  34,822,122 │   34,322,122 ║
@@ -55,6 +61,27 @@ arc-traces=${?ARC_TRACES}
 akka.cluster.sharding {
   passivation.simulator {
     runs = [
+      {
+        name = "OPT 250k"
+        shards = 100
+        regions = 10
+        pattern = arc-search-merged
+        strategy = optimal-25k
+      },
+      {
+        name = "OPT 500k"
+        shards = 100
+        regions = 10
+        pattern = arc-search-merged
+        strategy = optimal-50k
+      },
+      {
+        name = "OPT 1M"
+        shards = 100
+        regions = 10
+        pattern = arc-search-merged
+        strategy = optimal-100k
+      },
       {
         name = "LRU 250k"
         shards = 100
@@ -193,6 +220,27 @@ akka.cluster.sharding {
       }
     }
 
+    optimal-25k {
+      strategy = optimal
+      optimal {
+        per-region-limit = 25000
+      }
+    }
+
+    optimal-50k {
+      strategy = optimal
+      optimal {
+        per-region-limit = 50000
+      }
+    }
+
+    optimal-100k {
+      strategy = optimal
+      optimal {
+        per-region-limit = 100000
+      }
+    }
+
     lru-25k {
       strategy = least-recently-used
       least-recently-used {

akka-cluster-sharding/src/test/resources/lirs-trace-glimpse.conf

@@ -0,0 +1,506 @@
+#
+# Run the "glimpse" trace (gli.trace) from the authors of the LIRS algorithm.
+#
+# LIRS: An Efficient Low Inter-reference Recency Set Replacement Policy to Improve Buffer Cache Performance
+# Song Jiang and Xiaodong Zhang
+#
+# Download traces from: https://github.com/zhongch4g/LIRS2
+#
+# > akka-cluster-sharding/Test/runMain akka.cluster.sharding.passivation.simulator.Simulator lirs-trace-glimpse
+#
+#   ╔════════════╤═════════╤══════════╤═════════════╤══════════════╗
+#   ║        Run │  Active │ Accesses │ Activations │ Passivations ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    OPT 250 │ 17.70 % │    6,016 │       4,951 │        4,701 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    OPT 500 │ 34.33 % │    6,016 │       3,951 │        3,451 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   OPT 1000 │ 53.14 % │    6,016 │       2,819 │        1,819 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   OPT 1500 │ 57.95 % │    6,016 │       2,530 │        1,030 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    LRU 250 │  0.91 % │    6,016 │       5,961 │        5,711 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    LRU 500 │  0.95 % │    6,016 │       5,959 │        5,459 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   LRU 1000 │ 11.20 % │    6,016 │       5,342 │        4,342 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   LRU 1500 │ 36.55 % │    6,016 │       3,817 │        2,317 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║   SLRU 250 │  1.38 % │    6,016 │       5,933 │        5,683 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   SLRU 500 │  1.38 % │    6,016 │       5,933 │        5,433 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  SLRU 1000 │ 31.33 % │    6,016 │       4,131 │        3,131 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  SLRU 1500 │ 51.85 % │    6,016 │       2,897 │        1,397 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║  S4LRU 250 │  1.38 % │    6,016 │       5,933 │        5,693 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  S4LRU 500 │  1.38 % │    6,016 │       5,933 │        5,453 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║ S4LRU 1000 │ 19.70 % │    6,016 │       4,831 │        3,831 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║ S4LRU 1500 │ 48.02 % │    6,016 │       3,127 │        1,647 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    MRU 250 │ 14.78 % │    6,016 │       5,127 │        4,877 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    MRU 500 │ 31.40 % │    6,016 │       4,127 │        3,627 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   MRU 1000 │ 48.62 % │    6,016 │       3,091 │        2,091 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   MRU 1500 │ 53.37 % │    6,016 │       2,805 │        1,305 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    LFU 250 │  1.38 % │    6,016 │       5,933 │        5,683 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    LFU 500 │  1.38 % │    6,016 │       5,933 │        5,433 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   LFU 1000 │ 31.33 % │    6,016 │       4,131 │        3,131 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   LFU 1500 │ 51.85 % │    6,016 │       2,897 │        1,397 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║  LFUDA 250 │  1.11 % │    6,016 │       5,949 │        5,699 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  LFUDA 500 │  1.25 % │    6,016 │       5,941 │        5,441 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║ LFUDA 1000 │ 16.37 % │    6,016 │       5,031 │        4,031 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║ LFUDA 1500 │ 51.85 % │    6,016 │       2,897 │        1,397 ║
+#   ╚════════════╧═════════╧══════════╧═════════════╧══════════════╝
+#
+
+lirs-traces="lirs-traces"
+lirs-traces=${?LIRS_TRACES}
+
+akka.cluster.sharding {
+  passivation.simulator {
+    runs = [
+      {
+        name = "OPT 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = optimal-250
+      },
+      {
+        name = "OPT 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = optimal-500
+      },
+      {
+        name = "OPT 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = optimal-1000
+      },
+      {
+        name = "OPT 1500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = optimal-1500
+      },
+      {
+        name = "LRU 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lru-250
+      },
+      {
+        name = "LRU 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lru-500
+      },
+      {
+        name = "LRU 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lru-1000
+      },
+      {
+        name = "LRU 1500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lru-1500
+      },
+      {
+        name = "SLRU 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = slru-250
+      },
+      {
+        name = "SLRU 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = slru-500
+      },
+      {
+        name = "SLRU 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = slru-1000
+      },
+      {
+        name = "SLRU 1500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = slru-1500
+      },
+      {
+        name = "S4LRU 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = s4lru-250
+      },
+      {
+        name = "S4LRU 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = s4lru-500
+      },
+      {
+        name = "S4LRU 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = s4lru-1000
+      },
+      {
+        name = "S4LRU 1500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = s4lru-1500
+      },
+      {
+        name = "MRU 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = mru-250
+      },
+      {
+        name = "MRU 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = mru-500
+      },
+      {
+        name = "MRU 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = mru-1000
+      },
+      {
+        name = "MRU 1500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = mru-1500
+      },
+      {
+        name = "LFU 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lfu-250
+      },
+      {
+        name = "LFU 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lfu-500
+      },
+      {
+        name = "LFU 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lfu-1000
+      },
+      {
+        name = "LFU 1500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lfu-1500
+      },
+      {
+        name = "LFUDA 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lfuda-250
+      },
+      {
+        name = "LFUDA 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lfuda-500
+      },
+      {
+        name = "LFUDA 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lfuda-1000
+      },
+      {
+        name = "LFUDA 1500"
+        shards = 10
+        regions = 1
+        pattern = lirs-glimpse
+        strategy = lfuda-1500
+      },
+    ]
+
+    print-detailed-stats = true
+
+    lirs-glimpse {
+      pattern = trace
+      trace {
+        format = lirs
+        path = ${lirs-traces}"/gli.trace"
+      }
+    }
+
+    optimal-250 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 250
+      }
+    }
+
+    optimal-500 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 500
+      }
+    }
+
+    optimal-1000 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 1000
+      }
+    }
+
+    optimal-1500 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 1500
+      }
+    }
+
+    lru-250 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 250
+      }
+    }
+
+    lru-500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 500
+      }
+    }
+
+    lru-1000 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1000
+      }
+    }
+
+    lru-1500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1500
+      }
+    }
+
+    slru-250 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 250
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 500
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-1000 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1000
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-1500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1500
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    s4lru-250 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 250
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 500
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-1000 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1000
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-1500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1500
+        segmented.levels = 4
+      }
+    }
+
+    mru-250 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 250
+      }
+    }
+
+    mru-500 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 500
+      }
+    }
+
+    mru-1000 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 1000
+      }
+    }
+
+    mru-1500 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 1500
+      }
+    }
+
+    lfu-250 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 250
+      }
+    }
+
+    lfu-500 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 500
+      }
+    }
+
+    lfu-1000 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 1000
+      }
+    }
+
+    lfu-1500 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 1500
+      }
+    }
+
+    lfuda-250 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 250
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-500 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 500
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-1000 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 1000
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-1500 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 1500
+        dynamic-aging = on
+      }
+    }
+  }
+}

akka-cluster-sharding/src/test/resources/lirs-trace-multi.conf

@@ -0,0 +1,624 @@
+#
+# Run the "multi3" trace (multi3.trace) from the authors of the LIRS algorithm.
+#
+# LIRS: An Efficient Low Inter-reference Recency Set Replacement Policy to Improve Buffer Cache Performance
+# Song Jiang and Xiaodong Zhang
+#
+# Download traces from: https://github.com/zhongch4g/LIRS2
+#
+# > akka-cluster-sharding/Test/runMain akka.cluster.sharding.passivation.simulator.Simulator lirs-trace-multi
+#
+#   ╔════════════╤═════════╤══════════╤═════════════╤══════════════╗
+#   ║        Run │  Active │ Accesses │ Activations │ Passivations ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    OPT 100 │ 31.20 % │   30,241 │      20,807 │       20,707 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    OPT 200 │ 38.47 % │   30,241 │      18,607 │       18,407 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    OPT 400 │ 47.14 % │   30,241 │      15,986 │       15,586 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    OPT 800 │ 53.53 % │   30,241 │      14,054 │       13,254 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   OPT 1600 │ 64.14 % │   30,241 │      10,844 │        9,244 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    LRU 100 │  6.53 % │   30,241 │      28,266 │       28,166 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    LRU 200 │ 14.38 % │   30,241 │      25,891 │       25,691 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    LRU 400 │ 27.55 % │   30,241 │      21,909 │       21,509 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    LRU 800 │ 35.97 % │   30,241 │      19,364 │       18,564 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   LRU 1600 │ 44.23 % │   30,241 │      16,865 │       15,265 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║   SLRU 100 │  9.22 % │   30,241 │      27,454 │       27,354 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   SLRU 200 │ 22.41 % │   30,241 │      23,463 │       23,263 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   SLRU 400 │ 29.94 % │   30,241 │      21,186 │       20,786 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   SLRU 800 │ 37.30 % │   30,241 │      18,961 │       18,161 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  SLRU 1600 │ 46.51 % │   30,241 │      16,177 │       14,577 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║  S4LRU 100 │  8.43 % │   30,241 │      27,691 │       27,611 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  S4LRU 200 │ 22.62 % │   30,241 │      23,401 │       23,201 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  S4LRU 400 │ 30.10 % │   30,241 │      21,139 │       20,739 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  S4LRU 800 │ 37.30 % │   30,241 │      18,962 │       18,162 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║ S4LRU 1600 │ 46.51 % │   30,241 │      16,177 │       14,577 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    MRU 100 │  2.41 % │   30,241 │      29,512 │       29,412 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    MRU 200 │  4.20 % │   30,241 │      28,970 │       28,770 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    MRU 400 │  7.21 % │   30,241 │      28,062 │       27,662 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    MRU 800 │ 14.11 % │   30,241 │      25,973 │       25,173 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   MRU 1600 │ 26.31 % │   30,241 │      22,284 │       20,684 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    LFU 100 │  8.88 % │   30,241 │      27,557 │       27,457 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    LFU 200 │ 22.14 % │   30,241 │      23,547 │       23,347 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    LFU 400 │ 29.85 % │   30,241 │      21,213 │       20,813 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    LFU 800 │ 37.30 % │   30,241 │      18,961 │       18,161 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   LFU 1600 │ 46.51 % │   30,241 │      16,177 │       14,577 ║
+#   ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║  LFUDA 100 │ 10.16 % │   30,241 │      27,168 │       27,068 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  LFUDA 200 │ 22.99 % │   30,241 │      23,290 │       23,090 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  LFUDA 400 │ 30.50 % │   30,241 │      21,019 │       20,619 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  LFUDA 800 │ 37.25 % │   30,241 │      18,977 │       18,177 ║
+#   ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║ LFUDA 1600 │ 46.21 % │   30,241 │      16,267 │       14,667 ║
+#   ╚════════════╧═════════╧══════════╧═════════════╧══════════════╝
+#
+
+lirs-traces="lirs-traces"
+lirs-traces=${?LIRS_TRACES}
+
+akka.cluster.sharding {
+  passivation.simulator {
+    runs = [
+      {
+        name = "OPT 100"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = optimal-100
+      },
+      {
+        name = "OPT 200"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = optimal-200
+      },
+      {
+        name = "OPT 400"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = optimal-400
+      },
+      {
+        name = "OPT 800"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = optimal-800
+      },
+      {
+        name = "OPT 1600"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = optimal-1600
+      },
+      {
+        name = "LRU 100"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lru-100
+      },
+      {
+        name = "LRU 200"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lru-200
+      },
+      {
+        name = "LRU 400"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lru-400
+      },
+      {
+        name = "LRU 800"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lru-800
+      },
+      {
+        name = "LRU 1600"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lru-1600
+      },
+      {
+        name = "SLRU 100"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = slru-100
+      },
+      {
+        name = "SLRU 200"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = slru-200
+      },
+      {
+        name = "SLRU 400"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = slru-400
+      },
+      {
+        name = "SLRU 800"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = slru-800
+      },
+      {
+        name = "SLRU 1600"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = slru-1600
+      },
+      {
+        name = "S4LRU 100"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = s4lru-100
+      },
+      {
+        name = "S4LRU 200"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = s4lru-200
+      },
+      {
+        name = "S4LRU 400"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = s4lru-400
+      },
+      {
+        name = "S4LRU 800"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = s4lru-800
+      },
+      {
+        name = "S4LRU 1600"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = s4lru-1600
+      },
+      {
+        name = "MRU 100"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = mru-100
+      },
+      {
+        name = "MRU 200"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = mru-200
+      },
+      {
+        name = "MRU 400"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = mru-400
+      },
+      {
+        name = "MRU 800"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = mru-800
+      },
+      {
+        name = "MRU 1600"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = mru-1600
+      },
+      {
+        name = "LFU 100"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lfu-100
+      },
+      {
+        name = "LFU 200"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lfu-200
+      },
+      {
+        name = "LFU 400"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lfu-400
+      },
+      {
+        name = "LFU 800"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lfu-800
+      },
+      {
+        name = "LFU 1600"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lfu-1600
+      },
+      {
+        name = "LFUDA 100"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lfuda-100
+      },
+      {
+        name = "LFUDA 200"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lfuda-200
+      },
+      {
+        name = "LFUDA 400"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lfuda-400
+      },
+      {
+        name = "LFUDA 800"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lfuda-800
+      },
+      {
+        name = "LFUDA 1600"
+        shards = 10
+        regions = 1
+        pattern = lirs-multi3
+        strategy = lfuda-1600
+      },
+    ]
+
+    print-detailed-stats = true
+
+    lirs-multi3 {
+      pattern = trace
+      trace {
+        format = lirs
+        path = ${lirs-traces}"/multi3.trace"
+      }
+    }
+
+    optimal-100 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 100
+      }
+    }
+
+    optimal-200 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 200
+      }
+    }
+
+    optimal-400 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 400
+      }
+    }
+
+    optimal-800 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 800
+      }
+    }
+
+    optimal-1600 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 1600
+      }
+    }
+
+    lru-100 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 100
+      }
+    }
+
+    lru-200 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 200
+      }
+    }
+
+    lru-400 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 400
+      }
+    }
+
+    lru-800 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 800
+      }
+    }
+
+    lru-1600 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1600
+      }
+    }
+
+    slru-100 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 100
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-200 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 200
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-400 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 400
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-800 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 800
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-1600 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1600
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    s4lru-100 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 100
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-200 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 200
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-400 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 400
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-800 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 800
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-1600 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1600
+        segmented.levels = 4
+      }
+    }
+
+    mru-100 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 100
+      }
+    }
+
+    mru-200 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 200
+      }
+    }
+
+    mru-400 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 400
+      }
+    }
+
+    mru-800 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 800
+      }
+    }
+
+    mru-1600 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 1600
+      }
+    }
+
+    lfu-100 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 100
+      }
+    }
+
+    lfu-200 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 200
+      }
+    }
+
+    lfu-400 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 400
+      }
+    }
+
+    lfu-800 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 800
+      }
+    }
+
+    lfu-1600 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 1600
+      }
+    }
+
+    lfuda-100 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 100
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-200 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 200
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-400 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 400
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-800 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 800
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-1600 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 1600
+        dynamic-aging = on
+      }
+    }
+  }
+}

akka-cluster-sharding/src/test/resources/lirs-trace-postgres.conf

@@ -0,0 +1,506 @@
+#
+# Run the "postgres" trace (ps.trace) from the authors of the LIRS algorithm.
+#
+# LIRS: An Efficient Low Inter-reference Recency Set Replacement Policy to Improve Buffer Cache Performance
+# Song Jiang and Xiaodong Zhang
+#
+# Download traces from: https://github.com/zhongch4g/LIRS2
+#
+# > akka-cluster-sharding/Test/runMain akka.cluster.sharding.passivation.simulator.Simulator lirs-trace-postgres
+#
+# ╔════════════╤═════════╤══════════╤═════════════╤══════════════╗
+# ║        Run │  Active │ Accesses │ Activations │ Passivations ║
+# ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+# ║    OPT 125 │ 35.16 % │   10,448 │       6,774 │        6,654 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║    OPT 250 │ 53.33 % │   10,448 │       4,876 │        4,626 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║    OPT 500 │ 58.12 % │   10,448 │       4,376 │        3,876 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║   OPT 1000 │ 67.69 % │   10,448 │       3,376 │        2,376 ║
+# ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+# ║    LRU 125 │ 12.19 % │   10,448 │       9,174 │        9,054 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║    LRU 250 │ 13.95 % │   10,448 │       8,991 │        8,741 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║    LRU 500 │ 48.55 % │   10,448 │       5,376 │        4,876 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║   LRU 1000 │ 48.55 % │   10,448 │       5,376 │        4,376 ║
+# ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+# ║   SLRU 125 │  9.34 % │   10,448 │       9,472 │        9,362 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║   SLRU 250 │ 16.80 % │   10,448 │       8,693 │        8,443 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║   SLRU 500 │ 52.59 % │   10,448 │       4,953 │        4,453 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║  SLRU 1000 │ 52.59 % │   10,448 │       4,953 │        3,953 ║
+# ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+# ║  S4LRU 125 │  9.34 % │   10,448 │       9,472 │        9,352 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║  S4LRU 250 │ 16.80 % │   10,448 │       8,693 │        8,453 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║  S4LRU 500 │ 51.95 % │   10,448 │       5,020 │        4,540 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║ S4LRU 1000 │ 52.59 % │   10,448 │       4,953 │        3,953 ║
+# ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+# ║    MRU 125 │ 14.23 % │   10,448 │       8,961 │        8,841 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║    MRU 250 │ 30.84 % │   10,448 │       7,226 │        6,976 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║    MRU 500 │ 45.67 % │   10,448 │       5,676 │        5,176 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║   MRU 1000 │ 64.41 % │   10,448 │       3,718 │        2,718 ║
+# ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+# ║    LFU 125 │  9.34 % │   10,448 │       9,472 │        9,352 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║    LFU 250 │ 16.80 % │   10,448 │       8,693 │        8,443 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║    LFU 500 │ 52.59 % │   10,448 │       4,953 │        4,453 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║   LFU 1000 │ 52.59 % │   10,448 │       4,953 │        3,953 ║
+# ╠════════════╪═════════╪══════════╪═════════════╪══════════════╣
+# ║  LFUDA 125 │ 12.89 % │   10,448 │       9,101 │        8,981 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║  LFUDA 250 │ 16.79 % │   10,448 │       8,694 │        8,444 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║  LFUDA 500 │ 52.58 % │   10,448 │       4,954 │        4,454 ║
+# ╟────────────┼─────────┼──────────┼─────────────┼──────────────╢
+# ║ LFUDA 1000 │ 52.58 % │   10,448 │       4,954 │        3,954 ║
+# ╚════════════╧═════════╧══════════╧═════════════╧══════════════╝
+#
+
+lirs-traces="lirs-traces"
+lirs-traces=${?LIRS_TRACES}
+
+akka.cluster.sharding {
+  passivation.simulator {
+    runs = [
+      {
+        name = "OPT 125"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = optimal-125
+      },
+      {
+        name = "OPT 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = optimal-250
+      },
+      {
+        name = "OPT 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = optimal-500
+      },
+      {
+        name = "OPT 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = optimal-1000
+      },
+      {
+        name = "LRU 125"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lru-125
+      },
+      {
+        name = "LRU 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lru-250
+      },
+      {
+        name = "LRU 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lru-500
+      },
+      {
+        name = "LRU 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lru-1000
+      },
+      {
+        name = "SLRU 125"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = slru-125
+      },
+      {
+        name = "SLRU 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = slru-250
+      },
+      {
+        name = "SLRU 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = slru-500
+      },
+      {
+        name = "SLRU 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = slru-1000
+      },
+      {
+        name = "S4LRU 125"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = s4lru-125
+      },
+      {
+        name = "S4LRU 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = s4lru-250
+      },
+      {
+        name = "S4LRU 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = s4lru-500
+      },
+      {
+        name = "S4LRU 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = s4lru-1000
+      },
+      {
+        name = "MRU 125"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = mru-125
+      },
+      {
+        name = "MRU 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = mru-250
+      },
+      {
+        name = "MRU 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = mru-500
+      },
+      {
+        name = "MRU 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = mru-1000
+      },
+      {
+        name = "LFU 125"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lfu-125
+      },
+      {
+        name = "LFU 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lfu-250
+      },
+      {
+        name = "LFU 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lfu-500
+      },
+      {
+        name = "LFU 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lfu-1000
+      },
+      {
+        name = "LFUDA 125"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lfuda-125
+      },
+      {
+        name = "LFUDA 250"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lfuda-250
+      },
+      {
+        name = "LFUDA 500"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lfuda-500
+      },
+      {
+        name = "LFUDA 1000"
+        shards = 10
+        regions = 1
+        pattern = lirs-postgres
+        strategy = lfuda-1000
+      },
+    ]
+
+    print-detailed-stats = true
+
+    lirs-postgres {
+      pattern = trace
+      trace {
+        format = lirs
+        path = ${lirs-traces}"/ps.trace"
+      }
+    }
+
+    optimal-125 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 125
+      }
+    }
+
+    optimal-250 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 250
+      }
+    }
+
+    optimal-500 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 500
+      }
+    }
+
+    optimal-1000 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 1000
+      }
+    }
+
+    lru-125 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 125
+      }
+    }
+
+    lru-250 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 250
+      }
+    }
+
+    lru-500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 500
+      }
+    }
+
+    lru-1000 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1000
+      }
+    }
+
+    slru-125 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 125
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-250 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 250
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 500
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-1000 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1000
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    s4lru-125 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 125
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-250 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 250
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 500
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-1000 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 1000
+        segmented.levels = 4
+      }
+    }
+
+    mru-125 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 125
+      }
+    }
+
+    mru-250 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 250
+      }
+    }
+
+    mru-500 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 500
+      }
+    }
+
+    mru-1000 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 1000
+      }
+    }
+
+    lfu-125 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 125
+      }
+    }
+
+    lfu-250 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 250
+      }
+    }
+
+    lfu-500 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 500
+      }
+    }
+
+    lfu-1000 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 1000
+      }
+    }
+
+    lfuda-125 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 125
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-250 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 250
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-500 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 500
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-1000 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 1000
+        dynamic-aging = on
+      }
+    }
+  }
+}

akka-cluster-sharding/src/test/resources/lirs2-trace-w106.conf

@@ -0,0 +1,509 @@
+#
+# Run the "w106" binary trace (w106.trace) from the authors of the LIRS2 algorithm.
+#
+# LIRS2: An Improved LIRS Replacement Algorithm
+# Chen Zhong, Xingsheng Zhao, and Song Jiang
+#
+# Download traces from: https://github.com/zhongch4g/LIRS2
+#
+# This trace is a week-long virtual disk trace collected by CloudPhysics's caching analytics service.
+# The trace has just over 275k unique ids. The most popular 100 ids account for around 34% of accesses.
+#
+# > akka-cluster-sharding/Test/runMain akka.cluster.sharding.passivation.simulator.Simulator lirs2-trace-w106
+#
+#   ╔═══════════╤═════════╤═══════════╤═════════════╤══════════════╗
+#   ║       Run │  Active │  Accesses │ Activations │ Passivations ║
+#   ╠═══════════╪═════════╪═══════════╪═════════════╪══════════════╣
+#   ║    OPT 50 │ 57.92 % │ 5,292,456 │   2,226,826 │    2,226,776 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   OPT 100 │ 66.17 % │ 5,292,456 │   1,790,310 │    1,790,210 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   OPT 200 │ 71.69 % │ 5,292,456 │   1,498,368 │    1,498,168 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   OPT 500 │ 77.20 % │ 5,292,456 │   1,206,445 │    1,205,945 ║
+#   ╠═══════════╪═════════╪═══════════╪═════════════╪══════════════╣
+#   ║    LRU 50 │ 45.35 % │ 5,292,456 │   2,892,538 │    2,892,488 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   LRU 100 │ 53.47 % │ 5,292,456 │   2,462,659 │    2,462,559 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   LRU 200 │ 64.96 % │ 5,292,456 │   1,854,353 │    1,854,153 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   LRU 500 │ 70.97 % │ 5,292,456 │   1,536,203 │    1,535,703 ║
+#   ╠═══════════╪═════════╪═══════════╪═════════════╪══════════════╣
+#   ║   SLRU 50 │ 41.44 % │ 5,292,456 │   3,099,112 │    3,099,062 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║  SLRU 100 │ 52.52 % │ 5,292,456 │   2,513,049 │    2,512,949 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║  SLRU 200 │ 60.42 % │ 5,292,456 │   2,094,936 │    2,094,736 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║  SLRU 500 │ 70.02 % │ 5,292,456 │   1,586,665 │    1,586,165 ║
+#   ╠═══════════╪═════════╪═══════════╪═════════════╪══════════════╣
+#   ║  S4LRU 50 │ 39.87 % │ 5,292,456 │   3,182,347 │    3,182,307 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║ S4LRU 100 │ 54.30 % │ 5,292,456 │   2,418,459 │    2,418,359 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║ S4LRU 200 │ 63.50 % │ 5,292,456 │   1,931,759 │    1,931,559 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║ S4LRU 500 │ 70.68 % │ 5,292,456 │   1,551,818 │    1,551,318 ║
+#   ╠═══════════╪═════════╪═══════════╪═════════════╪══════════════╣
+#   ║    MRU 50 │ 22.23 % │ 5,292,456 │   4,116,089 │    4,116,039 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   MRU 100 │ 22.36 % │ 5,292,456 │   4,109,089 │    4,108,989 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   MRU 200 │ 22.68 % │ 5,292,456 │   4,092,384 │    4,092,184 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   MRU 500 │ 23.53 % │ 5,292,456 │   4,046,928 │    4,046,428 ║
+#   ╠═══════════╪═════════╪═══════════╪═════════════╪══════════════╣
+#   ║    LFU 50 │ 35.92 % │ 5,292,456 │   3,391,594 │    3,391,544 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   LFU 100 │ 42.52 % │ 5,292,456 │   3,041,915 │    3,041,815 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   LFU 200 │ 48.42 % │ 5,292,456 │   2,729,711 │    2,729,511 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║   LFU 500 │ 53.57 % │ 5,292,456 │   2,457,445 │    2,456,945 ║
+#   ╠═══════════╪═════════╪═══════════╪═════════════╪══════════════╣
+#   ║  LFUDA 50 │ 46.11 % │ 5,292,456 │   2,851,965 │    2,851,915 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║ LFUDA 100 │ 55.62 % │ 5,292,456 │   2,348,665 │    2,348,565 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║ LFUDA 200 │ 64.83 % │ 5,292,456 │   1,861,307 │    1,861,107 ║
+#   ╟───────────┼─────────┼───────────┼─────────────┼──────────────╢
+#   ║ LFUDA 500 │ 71.38 % │ 5,292,456 │   1,514,631 │    1,514,131 ║
+#   ╚═══════════╧═════════╧═══════════╧═════════════╧══════════════╝
+#
+
+lirs2-traces="lirs2-traces"
+lirs2-traces=${?LIRS2_TRACES}
+
+akka.cluster.sharding {
+  passivation.simulator {
+    runs = [
+      {
+        name = "OPT 50"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = optimal-50
+      },
+      {
+        name = "OPT 100"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = optimal-100
+      },
+      {
+        name = "OPT 200"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = optimal-200
+      },
+      {
+        name = "OPT 500"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = optimal-500
+      },
+      {
+        name = "LRU 50"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lru-50
+      },
+      {
+        name = "LRU 100"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lru-100
+      },
+      {
+        name = "LRU 200"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lru-200
+      },
+      {
+        name = "LRU 500"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lru-500
+      },
+      {
+        name = "SLRU 50"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = slru-50
+      },
+      {
+        name = "SLRU 100"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = slru-100
+      },
+      {
+        name = "SLRU 200"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = slru-200
+      },
+      {
+        name = "SLRU 500"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = slru-500
+      },
+      {
+        name = "S4LRU 50"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = s4lru-50
+      },
+      {
+        name = "S4LRU 100"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = s4lru-100
+      },
+      {
+        name = "S4LRU 200"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = s4lru-200
+      },
+      {
+        name = "S4LRU 500"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = s4lru-500
+      },
+      {
+        name = "MRU 50"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = mru-50
+      },
+      {
+        name = "MRU 100"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = mru-100
+      },
+      {
+        name = "MRU 200"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = mru-200
+      },
+      {
+        name = "MRU 500"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = mru-500
+      },
+      {
+        name = "LFU 50"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lfu-50
+      },
+      {
+        name = "LFU 100"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lfu-100
+      },
+      {
+        name = "LFU 200"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lfu-200
+      },
+      {
+        name = "LFU 500"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lfu-500
+      },
+      {
+        name = "LFUDA 50"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lfuda-50
+      },
+      {
+        name = "LFUDA 100"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lfuda-100
+      },
+      {
+        name = "LFUDA 200"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lfuda-200
+      },
+      {
+        name = "LFUDA 500"
+        shards = 5
+        regions = 1
+        pattern = lirs2-w106
+        strategy = lfuda-500
+      },
+    ]
+
+    print-detailed-stats = true
+
+    lirs2-w106 {
+      pattern = trace
+      trace {
+        format = lirs2
+        path = ${lirs2-traces}"/w106.trace"
+      }
+    }
+
+    optimal-50 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 50
+      }
+    }
+
+    optimal-100 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 100
+      }
+    }
+
+    optimal-200 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 200
+      }
+    }
+
+    optimal-500 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 500
+      }
+    }
+
+    lru-50 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 50
+      }
+    }
+
+    lru-100 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 100
+      }
+    }
+
+    lru-200 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 200
+      }
+    }
+
+    lru-500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 500
+      }
+    }
+
+    slru-50 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 50
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-100 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 100
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-200 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 200
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 500
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    s4lru-50 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 50
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-100 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 100
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-200 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 200
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-500 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 500
+        segmented.levels = 4
+      }
+    }
+
+    mru-50 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 50
+      }
+    }
+
+    mru-100 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 100
+      }
+    }
+
+    mru-200 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 200
+      }
+    }
+
+    mru-500 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 500
+      }
+    }
+
+    lfu-50 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 50
+      }
+    }
+
+    lfu-100 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 100
+      }
+    }
+
+    lfu-200 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 200
+      }
+    }
+
+    lfu-500 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 500
+      }
+    }
+
+    lfuda-50 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 50
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-100 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 100
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-200 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 200
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-500 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 500
+        dynamic-aging = on
+      }
+    }
+  }
+}

akka-cluster-sharding/src/test/resources/synthetic-zipfian.conf

@@ -8,6 +8,8 @@
 #   ╔════════════╤═════════╤════════════╤═════════════╤══════════════╗
 #   ║        Run │  Active │   Accesses │ Activations │ Passivations ║
 #   ╠════════════╪═════════╪════════════╪═════════════╪══════════════╣
+#   ║   OPT 100k │ 53.75 % │ 50,000,000 │  23,125,433 │   23,025,433 ║
+#   ╟────────────┼─────────┼────────────┼─────────────┼──────────────╢
 #   ║   LRU 100k │ 40.47 % │ 50,000,000 │  29,764,380 │   29,664,380 ║
 #   ╟────────────┼─────────┼────────────┼─────────────┼──────────────╢
 #   ║  SLRU 100k │ 47.14 % │ 50,000,000 │  26,428,026 │   26,328,026 ║
@@ -26,6 +28,8 @@
 #   ╔════════════╤═════════╤════════════╤═════════════╤══════════════╗
 #   ║        Run │  Active │   Accesses │ Activations │ Passivations ║
 #   ╠════════════╪═════════╪════════════╪═════════════╪══════════════╣
+#   ║   OPT 100k │ 32.31 % │ 50,000,000 │  33,846,785 │   33,746,785 ║
+#   ╟────────────┼─────────┼────────────┼─────────────┼──────────────╢
 #   ║   LRU 100k │ 22.50 % │ 50,000,000 │  38,749,623 │   38,649,623 ║
 #   ╟────────────┼─────────┼────────────┼─────────────┼──────────────╢
 #   ║  SLRU 100k │ 22.63 % │ 50,000,000 │  38,682,890 │   38,582,890 ║
@@ -43,6 +47,14 @@
 akka.cluster.sharding {
   passivation.simulator {
     runs = [
+      {
+        name = "OPT 100k"
+        shards = 100
+        regions = 10
+        pattern = scrambled-zipfian
+        # pattern = shifting-scrambled-zipfian
+        strategy = optimal-10k
+      },
       {
         name = "LRU 100k"
         shards = 100
@@ -126,6 +138,15 @@ akka.cluster.sharding {
       }
     }
 
+    # Optimal (clairvoyant) strategy with 10k limit in each of 10 regions
+    # total limit across cluster of 100k (1% of id space)
+    optimal-10k {
+      strategy = optimal
+      optimal {
+        per-region-limit = 10000
+      }
+    }
+
     # LRU strategy with 10k limit in each of 10 regions
     # total limit across cluster of 100k (1% of id space)
     lru-10k {

akka-cluster-sharding/src/test/resources/text-moby-dick.conf

@@ -0,0 +1,384 @@
+#
+# Run against the text of Moby Dick, for a natural zipfian-like distribution.
+#
+# Text can be downloaded from: https://www.gutenberg.org/files/2701/2701-0.txt
+#
+# > akka-cluster-sharding/Test/runMain akka.cluster.sharding.passivation.simulator.Simulator text-moby-dick
+#
+#   ╔═══════════╤═════════╤══════════╤═════════════╤══════════════╗
+#   ║       Run │  Active │ Accesses │ Activations │ Passivations ║
+#   ╠═══════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    OPT 25 │ 45.52 % │  216,904 │     118,161 │      118,136 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    OPT 50 │ 54.52 % │  216,904 │      98,658 │       98,608 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   OPT 100 │ 62.62 % │  216,904 │      81,073 │       80,973 ║
+#   ╠═══════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    LRU 25 │ 21.84 % │  216,904 │     169,542 │      169,517 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    LRU 50 │ 32.48 % │  216,904 │     146,444 │      146,394 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   LRU 100 │ 43.41 % │  216,904 │     122,750 │      122,650 ║
+#   ╠═══════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║   SLRU 25 │ 30.22 % │  216,904 │     151,349 │      151,324 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   SLRU 50 │ 40.14 % │  216,904 │     129,845 │      129,795 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  SLRU 100 │ 50.10 % │  216,904 │     108,241 │      108,141 ║
+#   ╠═══════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║  S4LRU 25 │ 30.19 % │  216,904 │     151,422 │      151,398 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  S4LRU 50 │ 40.15 % │  216,904 │     129,816 │      129,768 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║ S4LRU 100 │ 50.53 % │  216,904 │     107,304 │      107,204 ║
+#   ╠═══════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    MRU 25 │  0.30 % │  216,904 │     216,250 │      216,225 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    MRU 50 │  0.46 % │  216,904 │     215,899 │      215,849 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   MRU 100 │  0.71 % │  216,904 │     215,359 │      215,259 ║
+#   ╠═══════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║    LFU 25 │ 24.55 % │  216,904 │     163,651 │      163,626 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║    LFU 50 │ 33.91 % │  216,904 │     143,345 │      143,295 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║   LFU 100 │ 43.58 % │  216,904 │     122,378 │      122,278 ║
+#   ╠═══════════╪═════════╪══════════╪═════════════╪══════════════╣
+#   ║  LFUDA 25 │ 30.80 % │  216,904 │     150,106 │      150,081 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║  LFUDA 50 │ 40.90 % │  216,904 │     128,180 │      128,130 ║
+#   ╟───────────┼─────────┼──────────┼─────────────┼──────────────╢
+#   ║ LFUDA 100 │ 50.79 % │  216,904 │     106,731 │      106,631 ║
+#   ╚═══════════╧═════════╧══════════╧═════════════╧══════════════╝
+#
+
+text-traces="text-traces"
+text-traces=${?TEXT_TRACES}
+
+akka.cluster.sharding {
+  passivation.simulator {
+    runs = [
+      {
+        name = "OPT 25"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = optimal-25
+      },
+      {
+        name = "OPT 50"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = optimal-50
+      },
+      {
+        name = "OPT 100"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = optimal-100
+      },
+      {
+        name = "LRU 25"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = lru-25
+      },
+      {
+        name = "LRU 50"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = lru-50
+      },
+      {
+        name = "LRU 100"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = lru-100
+      },
+      {
+        name = "SLRU 25"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = slru-25
+      },
+      {
+        name = "SLRU 50"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = slru-50
+      },
+      {
+        name = "SLRU 100"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = slru-100
+      },
+      {
+        name = "S4LRU 25"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = s4lru-25
+      },
+      {
+        name = "S4LRU 50"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = s4lru-50
+      },
+      {
+        name = "S4LRU 100"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = s4lru-100
+      },
+      {
+        name = "MRU 25"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = mru-25
+      },
+      {
+        name = "MRU 50"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = mru-50
+      },
+      {
+        name = "MRU 100"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = mru-100
+      },
+      {
+        name = "LFU 25"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = lfu-25
+      },
+      {
+        name = "LFU 50"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = lfu-50
+      },
+      {
+        name = "LFU 100"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = lfu-100
+      },
+      {
+        name = "LFUDA 25"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = lfuda-25
+      },
+      {
+        name = "LFUDA 50"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = lfuda-50
+      },
+      {
+        name = "LFUDA 100"
+        shards = 1
+        regions = 1
+        pattern = moby-dick
+        strategy = lfuda-100
+      },
+    ]
+
+    # Moby Dick text as a trace
+    moby-dick {
+      pattern = trace
+      trace {
+        format = text
+        path = ${text-traces}"/moby-dick.txt"
+      }
+    }
+
+    optimal-25 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 25
+      }
+    }
+
+    optimal-50 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 50
+      }
+    }
+
+    optimal-100 {
+      strategy = optimal
+      optimal {
+        per-region-limit = 100
+      }
+    }
+
+    lru-25 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 25
+      }
+    }
+
+    lru-50 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 50
+      }
+    }
+
+    lru-100 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 100
+      }
+    }
+
+    slru-25 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 25
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-50 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 50
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    slru-100 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 100
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    s4lru-25 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 25
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-50 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 50
+        segmented.levels = 4
+      }
+    }
+
+    s4lru-100 {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 100
+        segmented.levels = 4
+      }
+    }
+
+    mru-25 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 25
+      }
+    }
+
+    mru-50 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 50
+      }
+    }
+
+    mru-100 {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 100
+      }
+    }
+
+    lfu-25 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 25
+      }
+    }
+
+    lfu-50 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 50
+      }
+    }
+
+    lfu-100 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 100
+      }
+    }
+
+    lfuda-25 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 25
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-50 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 50
+        dynamic-aging = on
+      }
+    }
+
+    lfuda-100 {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 100
+        dynamic-aging = on
+      }
+    }
+  }
+}

akka-cluster-sharding/src/test/resources/wikipedia-trace-2018.conf

@@ -0,0 +1,141 @@
+#
+# Run the 14-day Wikipedia trace from 2018 (wiki2018.tr) from the LRB simulator.
+#
+# Learning Relaxed Belady for Content Distribution Network Caching
+# Zhenyu Song, Daniel S. Berger, Kai Li, Wyatt Lloyd
+#
+# Download traces from the simulator (uncompressed trace is 54 GB):
+# https://github.com/sunnyszy/lrb#traces
+#
+# Trace is 2.8 billion accesses with around 37.5 million unique ids.
+# Active entity limit of 100k is just over 0.1% of the id space.
+# The most popular 100k ids account for almost half of the accesses.
+#
+# > akka-cluster-sharding/Test/runMain akka.cluster.sharding.passivation.simulator.Simulator wikipedia-trace-2018
+#
+#   ╔════════════╤═════════╤═══════════════╤═══════════════╤═══════════════╗
+#   ║        Run │  Active │      Accesses │   Activations │  Passivations ║
+#   ╠════════════╪═════════╪═══════════════╪═══════════════╪═══════════════╣
+#   ║   LRU 100k │ 53.48 % │ 2,800,000,000 │ 1,302,519,161 │ 1,302,419,161 ║
+#   ╟────────────┼─────────┼───────────────┼───────────────┼───────────────╢
+#   ║  SLRU 100k │ 60.89 % │ 2,800,000,000 │ 1,095,063,465 │ 1,094,963,465 ║
+#   ╟────────────┼─────────┼───────────────┼───────────────┼───────────────╢
+#   ║ S4LRU 100k │ 60.66 % │ 2,800,000,000 │ 1,101,617,318 │ 1,101,517,318 ║
+#   ╟────────────┼─────────┼───────────────┼───────────────┼───────────────╢
+#   ║   MRU 100k │  5.70 % │ 2,800,000,000 │ 2,640,279,048 │ 2,640,179,048 ║
+#   ╟────────────┼─────────┼───────────────┼───────────────┼───────────────╢
+#   ║   LFU 100k │ 58.17 % │ 2,800,000,000 │ 1,171,104,161 │ 1,171,004,161 ║
+#   ╟────────────┼─────────┼───────────────┼───────────────┼───────────────╢
+#   ║ LFUDA 100k │ 60.01 % │ 2,800,000,000 │ 1,119,687,614 │ 1,119,587,614 ║
+#   ╚════════════╧═════════╧═══════════════╧═══════════════╧═══════════════╝
+#
+
+wiki-traces="wiki-traces"
+wiki-traces=${?WIKI_TRACES}
+
+akka.cluster.sharding {
+  passivation.simulator {
+    runs = [
+      {
+        name = "LRU 100k"
+        shards = 100
+        regions = 10
+        pattern = wiki-2018
+        strategy = lru-10k
+      },
+      {
+        name = "SLRU 100k"
+        shards = 100
+        regions = 10
+        pattern = wiki-2018
+        strategy = slru-10k
+      },
+      {
+        name = "S4LRU 100k"
+        shards = 100
+        regions = 10
+        pattern = wiki-2018
+        strategy = s4lru-10k
+      },
+      {
+        name = "MRU 100k"
+        shards = 100
+        regions = 10
+        pattern = wiki-2018
+        strategy = mru-10k
+      },
+      {
+        name = "LFU 100k"
+        shards = 100
+        regions = 10
+        pattern = wiki-2018
+        strategy = lfu-10k
+      },
+      {
+        name = "LFUDA 100k"
+        shards = 100
+        regions = 10
+        pattern = wiki-2018
+        strategy = lfuda-10k
+      },
+    ]
+
+    print-detailed-stats = true
+
+    wiki-2018 {
+      pattern = trace
+      trace {
+        format = wikipedia
+        path = ${wiki-traces}"/wiki2018.tr"
+      }
+    }
+
+    lru-10k {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 10000
+      }
+    }
+
+    slru-10k {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 10000
+        segmented {
+          levels = 2
+          proportions = [0.2, 0.8]
+        }
+      }
+    }
+
+    s4lru-10k {
+      strategy = least-recently-used
+      least-recently-used {
+        per-region-limit = 10000
+        segmented.levels = 4
+      }
+    }
+
+    mru-10k {
+      strategy = most-recently-used
+      most-recently-used {
+        per-region-limit = 10000
+      }
+    }
+
+    lfu-10k {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 10000
+      }
+    }
+
+    lfuda-10k {
+      strategy = least-frequently-used
+      least-frequently-used {
+        per-region-limit = 10000
+        dynamic-aging = on
+      }
+    }
+  }
+}

akka-cluster-sharding/src/test/scala/akka/cluster/sharding/passivation/simulator/AccessPattern.scala

@@ -12,10 +12,13 @@ import akka.util.ByteString
 import java.nio.file.Paths
 
 trait AccessPattern {
+  def isSynthetic: Boolean
   def entityIds: Source[EntityId, NotUsed]
 }
 
 abstract class SyntheticGenerator(events: Int) extends AccessPattern {
+  override val isSynthetic = true
+
   protected def nextValue(event: Int): Long
 
   protected def generateEntityIds: Source[Long, NotUsed] = Source.fromIterator(() => Iterator.from(1)).map(nextValue)
@@ -100,6 +103,8 @@ object SyntheticGenerator {
 }
 
 abstract class TraceFileReader(path: String) extends AccessPattern {
+  override val isSynthetic = false
+
   protected def lines: Source[String, NotUsed] =
     FileIO
       .fromPath(Paths.get(path))
@@ -117,6 +122,15 @@ object TraceFileReader {
     override def entityIds: Source[EntityId, NotUsed] = lines
   }
 
+  /**
+   * Text trace file format with a simple word tokenizer for ASCII text.
+   */
+  final class Text(path: String) extends TraceFileReader(path: String) {
+    override def entityIds: Source[EntityId, NotUsed] = lines.mapConcat { line =>
+      line.split("[^\\w-]+").filter(_.nonEmpty).map(_.toLowerCase)
+    }
+  }
+
   /**
    * Read traces provided with the "ARC" paper.
    * Nimrod Megiddo and Dharmendra S. Modha, "ARC: A Self-Tuning, Low Overhead Replacement Cache".
@@ -129,4 +143,39 @@ object TraceFileReader {
       (startId until (startId + numberOfIds)).map(_.toString)
     }
   }
+
+  /**
+   * Read traces provided with the "LIRS" (or "LIRS2") paper:
+   * LIRS: An Efficient Low Inter-reference Recency Set Replacement Policy to Improve Buffer Cache Performance
+   * Song Jiang and Xiaodong Zhang
+   */
+  final class Lirs(path: String) extends TraceFileReader(path: String) {
+    override def entityIds: Source[EntityId, NotUsed] = lines // just simple id per line format
+  }
+
+  /**
+   * Read binary traces provided with the "LIRS2" paper:
+   * LIRS2: An Improved LIRS Replacement Algorithm
+   * Chen Zhong, Xingsheng Zhao, and Song Jiang
+   */
+  final class Lirs2(path: String) extends AccessPattern {
+    override val isSynthetic = false
+
+    override def entityIds: Source[EntityId, NotUsed] =
+      FileIO // binary file of unsigned ints
+        .fromPath(Paths.get(path), chunkSize = 4)
+        .map(bytes => Integer.toUnsignedLong(bytes.toByteBuffer.getInt).toString)
+        .mapMaterializedValue(_ => NotUsed)
+  }
+
+  /**
+   * Read Wikipedia traces as used in the "LRB" paper:
+   * Learning Relaxed Belady for Content Distribution Network Caching
+   * Zhenyu Song, Daniel S. Berger, Kai Li, Wyatt Lloyd
+   */
+  final class Wikipedia(path: String) extends TraceFileReader(path: String) {
+    override def entityIds: Source[EntityId, NotUsed] = lines.map { line =>
+      line.split(" ")(1) // second number is the id
+    }
+  }
 }

akka-cluster-sharding/src/test/scala/akka/cluster/sharding/passivation/simulator/Simulator.scala

@@ -14,6 +14,7 @@ import akka.cluster.sharding.internal.{
   SegmentedLeastRecentlyUsedEntityPassivationStrategy
 }
 import akka.stream.scaladsl.{ Flow, Source }
+import akka.util.OptionVal
 import com.typesafe.config.ConfigFactory
 
 import scala.collection.{ immutable, mutable }
@@ -66,7 +67,7 @@ object Simulator {
       numberOfShards: Int,
       numberOfRegions: Int,
       accessPattern: AccessPattern,
-      createStrategy: () => EntityPassivationStrategy)
+      strategyCreator: StrategyCreator)
 
   object Simulation {
     def apply(runSettings: SimulatorSettings.RunSettings): Simulation =
@@ -75,7 +76,7 @@ object Simulator {
         numberOfShards = runSettings.shards,
         numberOfRegions = runSettings.regions,
         accessPattern = accessPattern(runSettings),
-        createStrategy = strategyCreator(runSettings))
+        strategyCreator = strategyCreator(runSettings))
 
     def accessPattern(runSettings: SimulatorSettings.RunSettings): AccessPattern = runSettings.pattern match {
       case SimulatorSettings.PatternSettings.Synthetic(generator, events) =>
@@ -98,21 +99,25 @@ object Simulator {
       case SimulatorSettings.PatternSettings.Trace(path, format) =>
         format match {
           case "arc"       => new TraceFileReader.Arc(path)
+          case "lirs"      => new TraceFileReader.Lirs(path)
+          case "lirs2"     => new TraceFileReader.Lirs2(path)
           case "simple"    => new TraceFileReader.Simple(path)
+          case "text"      => new TraceFileReader.Text(path)
+          case "wikipedia" => new TraceFileReader.Wikipedia(path)
           case _           => sys.error(s"Unknown trace file format [$format]")
         }
     }
 
-    def strategyCreator(runSettings: SimulatorSettings.RunSettings): () => EntityPassivationStrategy =
+    def strategyCreator(runSettings: SimulatorSettings.RunSettings): StrategyCreator =
       runSettings.strategy match {
-        case SimulatorSettings.StrategySettings.LeastRecentlyUsed(perRegionLimit, Nil) =>
+        case SimulatorSettings.StrategySettings.Optimal(perRegionLimit) =>
-          () => new LeastRecentlyUsedEntityPassivationStrategy(perRegionLimit, idleCheck = None)
+          new ClairvoyantStrategyCreator(perRegionLimit)
         case SimulatorSettings.StrategySettings.LeastRecentlyUsed(perRegionLimit, segmented) =>
-          () => new SegmentedLeastRecentlyUsedEntityPassivationStrategy(perRegionLimit, segmented, idleCheck = None)
+          new LeastRecentlyUsedStrategyCreator(perRegionLimit, segmented)
         case SimulatorSettings.StrategySettings.MostRecentlyUsed(perRegionLimit) =>
-          () => new MostRecentlyUsedEntityPassivationStrategy(perRegionLimit, idleCheck = None)
+          new MostRecentlyUsedStrategyCreator(perRegionLimit)
         case SimulatorSettings.StrategySettings.LeastFrequentlyUsed(perRegionLimit, dynamicAging) =>
-          () => new LeastFrequentlyUsedEntityPassivationStrategy(perRegionLimit, dynamicAging, idleCheck = None)
+          new LeastFrequentlyUsedStrategyCreator(perRegionLimit, dynamicAging)
       }
   }
 
@@ -138,9 +143,29 @@ object Simulator {
   final case class Passivated(regionId: RegionId, shardId: ShardId, entityIds: immutable.Seq[EntityId]) extends Event
 
   def simulate(simulation: Simulation)(implicit system: ActorSystem): Future[ShardingStats] =
+    if (simulation.strategyCreator.requiresPreprocessing) runWithPreprocessing(simulation) else run(simulation)
+
+  def run(simulation: Simulation)(implicit system: ActorSystem): Future[ShardingStats] =
     simulation.accessPattern.entityIds
       .via(ShardAllocation(simulation.numberOfShards, simulation.numberOfRegions))
-      .via(ShardingState(simulation.createStrategy))
+      .via(ShardingState(simulation.strategyCreator))
+      .runWith(SimulatorStats())
+
+  // note: may need a lot of extra memory, if accesses from the simulation are collected during preprocessing
+  def runWithPreprocessing(simulation: Simulation)(implicit system: ActorSystem): Future[ShardingStats] =
+    simulation.accessPattern.entityIds
+      .via(ShardAllocation(simulation.numberOfShards, simulation.numberOfRegions))
+      .map(simulation.strategyCreator.preprocess) // note: mutable state in strategy creator
+      .fold(immutable.Queue.empty[Access])((collected, access) =>
+        if (simulation.accessPattern.isSynthetic) collected.enqueue(access) else collected)
+      .flatMapConcat(
+        collectedAccesses =>
+          if (simulation.accessPattern.isSynthetic)
+            Source(collectedAccesses) // use the exact same randomly generated accesses
+          else
+            simulation.accessPattern.entityIds.via( // re-read the access pattern
+              ShardAllocation(simulation.numberOfShards, simulation.numberOfRegions)))
+      .via(ShardingState(simulation.strategyCreator))
       .runWith(SimulatorStats())
 
   object ShardAllocation {
@@ -178,28 +203,31 @@ object Simulator {
   }
 
   object ShardingState {
-    def apply(createStrategy: () => EntityPassivationStrategy): Flow[Access, Event, NotUsed] =
+    def apply(strategyCreator: StrategyCreator): Flow[Access, Event, NotUsed] =
       Flow[Access].statefulMapConcat(() => {
-        val state = new ShardingState(createStrategy)
+        val state = new ShardingState(strategyCreator)
         access => state.process(access)
       })
   }
 
-  final class ShardingState(createStrategy: () => EntityPassivationStrategy) {
+  final class ShardingState(strategyCreator: StrategyCreator) {
     private val active = mutable.Map.empty[RegionId, mutable.Map[ShardId, ShardState]]
 
+    private def createShardState(regionId: RegionId, shardId: ShardId): ShardState =
+      new ShardState(regionId, shardId, strategyCreator.create(shardId))
+
     def process(access: Access): Seq[Event] = {
       val regionId = access.regionId
       val shardId = access.shardId
       val region = active.getOrElseUpdate(regionId, mutable.Map.empty)
       val alreadyActive = region.contains(shardId)
-      val shard = region.getOrElseUpdate(shardId, new ShardState(regionId, shardId, createStrategy()))
+      val shard = region.getOrElseUpdate(shardId, createShardState(regionId, shardId))
       val passivated = if (!alreadyActive) region.values.toSeq.flatMap(_.updated(region.size)) else Nil
       passivated ++ shard.accessed(access.entityId)
     }
   }
 
-  final class ShardState(regionId: RegionId, shardId: ShardId, strategy: EntityPassivationStrategy) {
+  final class ShardState(regionId: RegionId, shardId: ShardId, strategy: SimulatedStrategy) {
     private val activeEntities = mutable.Set.empty[EntityId]
 
     def updated(activeShards: Int): immutable.Seq[Event] = {
@@ -225,4 +253,121 @@ object Simulator {
       changes :+ Accessed(regionId, shardId, entityId)
     }
   }
+
+  sealed trait SimulatedStrategy {
+    def shardsUpdated(activeShards: Int): immutable.Seq[EntityId]
+    def entityTouched(id: EntityId): immutable.Seq[EntityId]
+  }
+
+  final class PassivationStrategy(strategy: EntityPassivationStrategy) extends SimulatedStrategy {
+    override def shardsUpdated(activeShards: Int): immutable.Seq[EntityId] = strategy.shardsUpdated(activeShards)
+    override def entityTouched(id: EntityId): immutable.Seq[EntityId] = strategy.entityTouched(id)
+  }
+
+  sealed trait StrategyCreator {
+    def create(shardId: ShardId): SimulatedStrategy
+    def requiresPreprocessing: Boolean
+    def preprocess(access: Access): Access
+  }
+
+  sealed abstract class PassivationStrategyCreator extends StrategyCreator {
+    override val requiresPreprocessing = false
+    override def preprocess(access: Access): Access = access
+  }
+
+  final class LeastRecentlyUsedStrategyCreator(perRegionLimit: Int, segmented: immutable.Seq[Double])
+      extends PassivationStrategyCreator {
+    override def create(shardId: ShardId): SimulatedStrategy =
+      new PassivationStrategy(
+        if (segmented.nonEmpty)
+          new SegmentedLeastRecentlyUsedEntityPassivationStrategy(perRegionLimit, segmented, idleCheck = None)
+        else new LeastRecentlyUsedEntityPassivationStrategy(perRegionLimit, idleCheck = None))
+  }
+
+  final class MostRecentlyUsedStrategyCreator(perRegionLimit: Int) extends PassivationStrategyCreator {
+    override def create(shardId: ShardId): SimulatedStrategy =
+      new PassivationStrategy(new MostRecentlyUsedEntityPassivationStrategy(perRegionLimit, idleCheck = None))
+  }
+
+  final class LeastFrequentlyUsedStrategyCreator(perRegionLimit: Int, dynamicAging: Boolean)
+      extends PassivationStrategyCreator {
+    override def create(shardId: ShardId): SimulatedStrategy =
+      new PassivationStrategy(
+        new LeastFrequentlyUsedEntityPassivationStrategy(perRegionLimit, dynamicAging, idleCheck = None))
+  }
+
+  // Clairvoyant passivation strategy using Bélády's algorithm.
+  // Record virtual access times per entity id on a first pass through the access pattern,
+  // to passivate entities that will not be accessed again for the furthest time in the future.
+  // Note: running this requires a lot of extra memory for large workloads.
+
+  final class ClairvoyantAccessRecorder {
+    private type AccessTime = Int
+    private var tick: AccessTime = 0
+    private val futureAccesses = mutable.Map.empty[EntityId, mutable.Queue[AccessTime]]
+
+    def accessed(id: EntityId): Unit = {
+      tick += 1
+      futureAccesses.getOrElseUpdate(id, mutable.Queue.empty[AccessTime]) += tick
+    }
+
+    def nextAccess(id: EntityId): OptionVal[AccessTime] = {
+      val accesses = futureAccesses(id)
+      if (accesses.nonEmpty) OptionVal.Some(accesses.head)
+      else {
+        futureAccesses -= id
+        OptionVal.none
+      }
+    }
+
+    def previousAccess(id: EntityId): AccessTime = futureAccesses(id).dequeue()
+  }
+
+  final class ClairvoyantStrategyCreator(perRegionLimit: Int) extends StrategyCreator {
+    override val requiresPreprocessing = true
+
+    private val recorders = mutable.Map.empty[ShardId, ClairvoyantAccessRecorder]
+
+    override def preprocess(access: Access): Access = {
+      recorders.getOrElseUpdate(access.shardId, new ClairvoyantAccessRecorder).accessed(access.entityId)
+      access
+    }
+
+    override def create(shardId: ShardId): SimulatedStrategy =
+      new ClairvoyantPassivationStrategy(perRegionLimit, recorders.getOrElse(shardId, new ClairvoyantAccessRecorder))
+  }
+
+  final class ClairvoyantPassivationStrategy(perRegionLimit: Int, recorder: ClairvoyantAccessRecorder)
+      extends SimulatedStrategy {
+
+    private type AccessTime = Int
+    private var perShardLimit: Int = perRegionLimit
+    private val nextAccess = mutable.TreeMap.empty[AccessTime, EntityId]
+    private var never: AccessTime = Int.MaxValue
+
+    override def shardsUpdated(activeShards: Int): immutable.Seq[EntityId] = {
+      perShardLimit = perRegionLimit / activeShards
+      passivateExcessEntities()
+    }
+
+    override def entityTouched(id: EntityId): immutable.Seq[EntityId] = {
+      nextAccess -= recorder.previousAccess(id)
+      recorder.nextAccess(id) match {
+        case OptionVal.Some(access) =>
+          nextAccess += access -> id
+        case _ =>
+          never -= 1
+          nextAccess += never -> id
+      }
+      passivateExcessEntities()
+    }
+
+    private def passivateExcessEntities(): immutable.Seq[EntityId] = {
+      val passivated = mutable.ListBuffer.empty[EntityId]
+      while (nextAccess.size > perShardLimit) {
+        nextAccess.remove(nextAccess.lastKey).foreach(passivated.+=)
+      }
+      passivated.result()
+    }
+  }
 }

akka-cluster-sharding/src/test/scala/akka/cluster/sharding/passivation/simulator/SimulatorSettings.scala

@@ -45,6 +45,7 @@ object SimulatorSettings {
   sealed trait StrategySettings
 
   object StrategySettings {
+    final case class Optimal(perRegionLimit: Int) extends StrategySettings
     final case class LeastRecentlyUsed(perRegionLimit: Int, segmented: immutable.Seq[Double]) extends StrategySettings
     final case class MostRecentlyUsed(perRegionLimit: Int) extends StrategySettings
     final case class LeastFrequentlyUsed(perRegionLimit: Int, dynamicAging: Boolean) extends StrategySettings
@@ -52,6 +53,7 @@ object SimulatorSettings {
     def apply(simulatorConfig: Config, strategy: String): StrategySettings = {
       val config = simulatorConfig.getConfig(strategy).withFallback(simulatorConfig.getConfig("strategy-defaults"))
       lowerCase(config.getString("strategy")) match {
+        case "optimal" => Optimal(config.getInt("optimal.per-region-limit"))
         case "least-recently-used" =>
           val limit = config.getInt("least-recently-used.per-region-limit")
           val segmented = lowerCase(config.getString("least-recently-used.segmented.levels")) match {

akka-cluster-sharding/src/test/scala/akka/cluster/sharding/passivation/simulator/SimulatorStats.scala

@@ -20,7 +20,7 @@ object SimulatorStats {
     }
 }
 
-final case class EntityStats(accesses: Int = 0, activations: Int = 0, passivations: Int = 0) {
+final case class EntityStats(accesses: Long = 0, activations: Long = 0, passivations: Long = 0) {
   def accessed(): EntityStats = copy(accesses + 1, activations, passivations)
   def activated(): EntityStats = copy(accesses, activations + 1, passivations)
   def passivated(n: Int): EntityStats = copy(accesses, activations, passivations + n)