handle trim

Author: Alex Peck

BitFaster.Caching.UnitTests/Lru/ConcurrentLruTests.cs

@@ -764,6 +764,27 @@ public void WhenItemRemovedFromWarmAfterWarmupItIsEagerlyCycledOut()
             lru.Metrics.Value.Evicted.Should().Be(0);
         }
 
+        [Fact]
+        public void WhenItemRemovedFromColdAfterWarmupItIsEagerlyCycledOut()
+        {
+            for (int i = 0; i < lru.Capacity; i++)
+            {
+                lru.GetOrAdd(i, valueFactory.Create);
+            }
+
+            Print();                                    // Hot [6,7,8] Warm [1,2,3] Cold [0,4,5]
+            lru.Metrics.Value.Evicted.Should().Be(0);
+
+            lru.GetOrAdd(0, valueFactory.Create);
+            lru.TryRemove(0);
+
+            lru.GetOrAdd(9, valueFactory.Create);
+
+            Print();                                    // Hot [7,8,9] Warm [1,2,3] Cold [4,5,6]
+
+            lru.Metrics.Value.Evicted.Should().Be(0);
+        }
+
         [Fact]
         public void WhenKeyDoesNotExistTryRemoveReturnsFalse()
         {
@@ -772,6 +793,29 @@ public void WhenKeyDoesNotExistTryRemoveReturnsFalse()
             lru.TryRemove(2).Should().BeFalse();
         }
 
+        [Fact]
+        public void WhenItemsAreRemovedTrimRemovesDeletedItemsFromQueues()
+        {
+            for (int i = 0; i < lru.Capacity; i++)
+            {
+                lru.GetOrAdd(i, valueFactory.Create);
+            }
+
+            Print();                  // Hot [6,7,8] Warm [1,2,3] Cold [0,4,5]
+
+            lru.TryRemove(0);
+            lru.TryRemove(1);
+            lru.TryRemove(6);
+
+            lru.Policy.Eviction.Value.Trim(1);
+
+            Print();                  // Hot [7,8] Warm [2,3] Cold [5]
+
+            lru.HotCount.Should().Be(2);
+            lru.WarmCount.Should().Be(2);
+            lru.ColdCount.Should().Be(1);
+        }
+
         [Fact]
         public void WhenRepeatedlyAddingAndRemovingSameValueLruRemainsInConsistentState()
         {

BitFaster.Caching.UnitTests/Lru/ConcurrentTLruTests.cs

@@ -5,11 +5,13 @@
 using Xunit;
 using System.Runtime.InteropServices;
 using BitFaster.Caching.UnitTests.Retry;
+using Xunit.Abstractions;
 
 namespace BitFaster.Caching.UnitTests.Lru
 {
     public class ConcurrentTLruTests
     {
+        private readonly ITestOutputHelper testOutputHelper;
         private readonly TimeSpan timeToLive = TimeSpan.FromMilliseconds(10);
         private readonly ICapacityPartition capacity = new EqualCapacityPartition(9);
         private ConcurrentTLru<int, string> lru;
@@ -31,8 +33,9 @@ public ConcurrentTLru<K, V> CreateTLru<K, V>(ICapacityPartition capacity, TimeSp
             return new ConcurrentTLru<K, V>(1, capacity, EqualityComparer<K>.Default, timeToLive);
         }
 
-        public ConcurrentTLruTests()
+        public ConcurrentTLruTests(ITestOutputHelper testOutputHelper)
         {
+            this.testOutputHelper = testOutputHelper;
             lru = CreateTLru<int, string>(capacity, timeToLive);
         }
 
@@ -315,6 +318,31 @@ public void WhenItemsAreExpiredEnumerateFiltersExpiredItems()
             );
         }
 
+        [Fact]
+        public void WhenItemsAreRemovedTrimExpiredRemovesDeletedItemsFromQueues()
+        {
+            lru = CreateTLru<int, string>(capacity, TimeSpan.FromMinutes(1));
+
+            for (int i = 0; i < lru.Capacity; i++)
+            {
+                lru.GetOrAdd(i, valueFactory.Create);
+            }
+
+            Print();                  // Hot [6,7,8] Warm [1,2,3] Cold [0,4,5]
+
+            lru.TryRemove(0);
+            lru.TryRemove(1);
+            lru.TryRemove(6);
+
+            lru.Policy.ExpireAfterWrite.Value.TrimExpired();
+
+            Print();                  // Hot [7,8] Warm [2,3] Cold [4,5]
+
+            lru.HotCount.Should().Be(2);
+            lru.WarmCount.Should().Be(2);
+            lru.ColdCount.Should().Be(2);
+        }
+
         [Fact]
         public void ConstructWithDefaultCtorReturnsCapacity()
         {
@@ -338,5 +366,12 @@ public void ConstructPartitionCtorReturnsCapacity()
 
             x.Capacity.Should().Be(3);
         }
+
+        private void Print()
+        {
+#if DEBUG
+            this.testOutputHelper.WriteLine(this.lru.FormatLruString());
+#endif
+        }
     }
 }

BitFaster.Caching/Lru/ConcurrentLruCore.cs

@@ -468,7 +468,7 @@ public void Trim(int itemCount)
             lock (this.dictionary)
             {
                 // first scan each queue for discardable items and remove them immediately. Note this can remove > itemCount items.
-                int itemsRemoved = this.itemPolicy.CanDiscard() ? TrimAllDiscardedItems() : 0;
+                int itemsRemoved = TrimAllDiscardedItems();
 
                 TrimLiveItems(itemsRemoved, itemCount, ItemRemovedReason.Trimmed);
             }
@@ -478,7 +478,10 @@ private void TrimExpired()
         {
             if (this.itemPolicy.CanDiscard())
             {
-                this.TrimAllDiscardedItems();
+                lock (this.dictionary)
+                {
+                    this.TrimAllDiscardedItems();
+                } 
             }
         }
 
@@ -501,12 +504,16 @@ int RemoveDiscardableItems(ConcurrentQueue<I> q, ref int queueCounter)
                     {
                         if (q.TryDequeue(out var item))
                         {
-                            if (this.itemPolicy.ShouldDiscard(item) | item.WasRemoved)
+                            if (this.itemPolicy.ShouldDiscard(item))
                             {
                                 Interlocked.Decrement(ref queueCounter);
                                 this.Move(item, ItemDestination.Remove, ItemRemovedReason.Trimmed);
                                 itemsRemoved++;
                             }
+                            else if (item.WasRemoved)
+                            {
+                                Interlocked.Decrement(ref queueCounter);
+                            }
                             else
                             {
                                 q.Enqueue(item);
@@ -548,8 +555,10 @@ private void TrimLiveItems(int itemsRemoved, int itemCount, ItemRemovedReason re
                         itemsRemoved++;
                         trimWarmAttempts = 0;
                     }
-
-                    TrimWarmOrHot(reason);
+                    else
+                    {
+                        TrimWarmOrHot(reason);
+                    }
                 }
                 else
                 {
@@ -829,7 +838,7 @@ IEnumerator IEnumerable.GetEnumerator()
         /// Format the LRU as a string by converting all the keys to strings.
         /// </summary>
         /// <returns>The LRU formatted as a string.</returns>
-        public string FormatLruString()
+        internal string FormatLruString()
         {
             var sb = new System.Text.StringBuilder();