LIRS cache: keep more non-resident entries

h2/src/main/org/h2/mvstore/cache/CacheLongKeyLIRS.java

@@ -55,7 +55,7 @@ public class CacheLongKeyLIRS<V> {
     private final int segmentShift;
     private final int segmentMask;
     private final int stackMoveDistance;
-    private final double nonResidentQueueSize;
+    private final int nonResidentQueueSize;
 
     /**
      * Create a new cache with the given memory size.
@@ -535,7 +535,7 @@ public class CacheLongKeyLIRS<V> {
          * The number of entries in the non-resident queue, as a factor of the
          * number of entries in the map.
          */
-        private final double nonResidentQueueSize;
+        private final int nonResidentQueueSize;
 
         /**
          * The stack of recently referenced elements. This includes all hot
@@ -581,7 +581,7 @@ public class CacheLongKeyLIRS<V> {
          * @param nonResidentQueueSize the non-resident queue size factor
          */
         Segment(long maxMemory, int stackMoveDistance, int len,
-                double nonResidentQueueSize) {
+                int nonResidentQueueSize) {
             setMaxMemory(maxMemory);
             this.stackMoveDistance = stackMoveDistance;
             this.nonResidentQueueSize = nonResidentQueueSize;
@@ -904,11 +904,13 @@ public class CacheLongKeyLIRS<V> {
                 e.memory = 0;
                 addToQueue(queue2, e);
                 // the size of the non-resident-cold entries needs to be limited
-                int maxQueue2Size = (int) (nonResidentQueueSize * mapSize);
-                while (queue2Size > maxQueue2Size) {
-                    e = queue2.queuePrev;
-                    int hash = getHash(e.key);
-                    remove(e.key, hash);
+                int maxQueue2Size = nonResidentQueueSize * (mapSize - queue2Size);
+                if (maxQueue2Size >= 0) {
+                    while (queue2Size > maxQueue2Size) {
+                        e = queue2.queuePrev;
+                        int hash = getHash(e.key);
+                        remove(e.key, hash);
+                    }
                 }
             }
         }
@@ -1165,15 +1167,16 @@ public class CacheLongKeyLIRS<V> {
         public int segmentCount = 16;
 
         /**
-         * How many other item are to be moved to the top of the stack before the current item is moved.
+         * How many other item are to be moved to the top of the stack before
+         * the current item is moved.
          */
         public int stackMoveDistance = 32;
 
         /**
          * The number of entries in the non-resident queue, as a factor of the
-         * number of entries in the map.
+         * number of all other entries in the map.
          */
-        public double nonResidentQueueSize = 0.5;
+        public int nonResidentQueueSize = 3;
 
     }
 

h2/src/test/org/h2/test/store/TestCacheLongKeyLIRS.java

@@ -114,7 +114,8 @@ public class TestCacheLongKeyLIRS extends TestBase {
         assertEquals(63, test.size() - test.sizeHot());
         // at most as many non-resident elements
         // as there are entries in the stack
-        assertEquals(999, test.sizeNonResident());
+        assertEquals(1000, test.size());
+        assertEquals(1000, test.sizeNonResident());
     }
 
     private void verifyMapSize(int elements, int expectedMapSize) {
@@ -323,8 +324,8 @@ public class TestCacheLongKeyLIRS extends TestBase {
             test.put(i, 10 * i);
         }
         assertEquals(100, test.size());
-        assertEquals(99, test.sizeNonResident());
-        assertEquals(93, test.sizeHot());
+        assertEquals(200, test.sizeNonResident());
+        assertEquals(90, test.sizeHot());
     }
 
     private void testLimitNonResident() {
@@ -332,8 +333,8 @@ public class TestCacheLongKeyLIRS extends TestBase {
         for (int i = 0; i < 20; i++) {
             test.put(i, 10 * i);
         }
-        verify(test, "mem: 4 stack: 19 18 17 16 3 2 1 " +
-                "cold: 19 non-resident: 18 17 16");
+        verify(test, "mem: 4 stack: 19 18 17 16 15 14 13 12 11 10 3 2 1 " +
+                "cold: 19 non-resident: 18 17 16 15 14 13 12 11 10");
     }
 
     private void testLimitMemory() {
@@ -344,21 +345,21 @@ public class TestCacheLongKeyLIRS extends TestBase {
         verify(test, "mem: 4 stack: 4 3 2 1 cold: 4 non-resident: 0");
         assertTrue("" + test.getUsedMemory(), test.getUsedMemory() <= 4);
         test.put(6, 60, 3);
-        verify(test, "mem: 4 stack: 6 3 cold: 6 non-resident: 2 1");
+        verify(test, "mem: 4 stack: 6 4 3 cold: 6 non-resident: 2 1 4");
         assertTrue("" + test.getUsedMemory(), test.getUsedMemory() <= 4);
         test.put(7, 70, 3);
-        verify(test, "mem: 4 stack: 7 6 3 cold: 7 non-resident: 6 2");
+        verify(test, "mem: 4 stack: 7 6 3 cold: 7 non-resident: 6 2 1");
         assertTrue("" + test.getUsedMemory(), test.getUsedMemory() <= 4);
         test.put(8, 80, 4);
-        verify(test, "mem: 4 stack: 8 cold: non-resident: 3");
+        verify(test, "mem: 4 stack: 8 cold: non-resident:");
         assertTrue("" + test.getUsedMemory(), test.getUsedMemory() <= 4);
     }
 
     private void testScanResistance() {
         boolean log = false;
         int size = 20;
-        // cache size 11 (10 hot, 1 cold)
-        CacheLongKeyLIRS<Integer> test = createCache(size / 2 + 1);
+        // cache size 11 (10 hot, 2 cold)
+        CacheLongKeyLIRS<Integer> test = createCache(size / 2 + 2);
         // init the cache with some dummy entries
         for (int i = 0; i < size; i++) {
             test.put(-i, -i * 10);
@@ -394,10 +395,10 @@ public class TestCacheLongKeyLIRS extends TestBase {
             }
             verify(test, null);
         }
-        // ensure 0..9 are hot, 10..18 are not resident, 19 is cold
+        // ensure 0..9 are hot, 10..17 are not resident, 18..19 are cold
         for (int i = 0; i < size; i++) {
             Integer x = test.get(i);
-            if (i < size / 2 || i == size - 1) {
+            if (i < size / 2 || i == size - 1 || i == size - 2) {
                 assertTrue("i: " + i, x != null);
                 assertEquals(i * 10, x.intValue());
             } else {