Improving cache tracker

microsoft · Feb 27, 2022 · 9ee8a26 · 9ee8a26
1 parent 72bd490
commit 9ee8a26
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Showing 2 changed files with 10 additions and 7 deletions.
diff --git a/cs/samples/MemOnlyCache/CacheSizeTracker.cs b/cs/samples/MemOnlyCache/CacheSizeTracker.cs
@@ -85,10 +85,13 @@ public void OnNext(IFasterScanIterator<CacheKey, CacheValue> iter)
             AddTrackedSize(-size);
 
             // Adjust empty page count to drive towards desired memory utilization
-            if (TotalSizeBytes > TargetSizeBytes && store.Log.AllocatableMemorySizeBytes >= store.Log.MemorySizeBytes)
-                store.Log.EmptyPageCount++;
-            else if (TotalSizeBytes < TargetSizeBytes && store.Log.AllocatableMemorySizeBytes <= store.Log.MemorySizeBytes)
-                store.Log.EmptyPageCount--;
+            if (store.Log.PageAllocationStabilized())
+            {
+                if (TotalSizeBytes > TargetSizeBytes)
+                    store.Log.EmptyPageCount++;
+                else
+                    store.Log.EmptyPageCount--;
+            }
         }
 
         /// <summary>

diff --git a/cs/src/core/Index/FASTER/LogAccessor.cs b/cs/src/core/Index/FASTER/LogAccessor.cs
@@ -92,14 +92,14 @@ public void SetEmptyPageCount(int pageCount, bool wait = false)
         public int BufferSize => allocator.BufferSize;
 
         /// <summary>
-        /// Actual memory used by log (not including heap objects)
+        /// Actual memory used by log (not including heap objects) and overflow pages
         /// </summary>
         public long MemorySizeBytes => ((long)(allocator.AllocatedPageCount + allocator.OverflowPageCount)) << allocator.LogPageSizeBits;
 
         /// <summary>
-        /// Memory allocatable on the log (not including heap objects)
+        /// Whether we have allocated exactly the requested number of pages on the log (based on BufferSize and EmptyPageCount)
         /// </summary>
-        public long AllocatableMemorySizeBytes => ((long)(allocator.BufferSize - allocator.EmptyPageCount + allocator.OverflowPageCount)) << allocator.LogPageSizeBits;
+        public bool PageAllocationStabilized() => allocator.AllocatedPageCount == allocator.BufferSize - allocator.EmptyPageCount + 1;
 
         /// <summary>
         /// Shift begin address to the provided untilAddress. Make sure address corresponds to record boundary if snapToPageStart is set to