MemoryAllocators can now say how much memory they have available

neo4j · Dec 11, 2017 · da2136f · da2136f
1 parent a68a942
commit da2136f
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Showing 4 changed files with 42 additions and 4 deletions.
diff --git a/community/io/src/main/java/org/neo4j/io/mem/GrabAllocator.java b/community/io/src/main/java/org/neo4j/io/mem/GrabAllocator.java
@@ -60,7 +60,7 @@ public final class GrabAllocator implements MemoryAllocator
     }
 
     @Override
-    public synchronized long sumUsedMemory()
+    public synchronized long usedMemory()
     {
         long sum = 0;
         Grab grab = grabs;
@@ -72,6 +72,18 @@ public synchronized long sumUsedMemory()
         return sum;
     }
 
+    @Override
+    public synchronized long availableMemory()
+    {
+        Grab grab = grabs;
+        long availableInCurrentGrab = 0;
+        if ( grab != null )
+        {
+            availableInCurrentGrab = grab.limit - grab.nextAlignedPointer;
+        }
+        return Math.max( memoryReserve, 0L ) + availableInCurrentGrab;
+    }
+
     @Override
     public synchronized long allocateAligned( long bytes )
     {

diff --git a/community/io/src/main/java/org/neo4j/io/mem/MemoryAllocator.java b/community/io/src/main/java/org/neo4j/io/mem/MemoryAllocator.java
@@ -32,7 +32,12 @@ static MemoryAllocator createAllocator( long expectedMaxMemory, long alignment )
     /**
      * @return The sum, in bytes, of all the memory currently allocating through this allocator.
      */
-    long sumUsedMemory();
+    long usedMemory();
+
+    /**
+     * @return The amount of available memory, in bytes.
+     */
+    long availableMemory();
 
     /**
      * Allocate a contiguous, aligned region of memory of the given size in bytes.

diff --git a/community/io/src/test/java/org/neo4j/io/mem/MemoryAllocatorTest.java b/community/io/src/test/java/org/neo4j/io/mem/MemoryAllocatorTest.java
@@ -23,7 +23,9 @@
 
 import org.neo4j.unsafe.impl.internal.dragons.UnsafeUtil;
 
+import static org.hamcrest.Matchers.greaterThanOrEqualTo;
 import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.lessThanOrEqualTo;
 import static org.hamcrest.Matchers.not;
 import static org.junit.Assert.assertThat;
 
@@ -78,4 +80,23 @@ public void mustBeAbleToAllocateSlabsLargerThanGrabSize() throws Exception
         assertThat( largeBlock, is( not( 0L ) ) );
         assertThat( page2, is( not( 0L ) ) );
     }
+
+    @Test
+    public void allocatingMustIncreaseMemoryUsedAndDecreaseAvailableMemory() throws Exception
+    {
+        MemoryAllocator mman = createAllocator( 8192, 1 );
+        assertThat( mman.usedMemory(), is( 0L ) );
+        assertThat( mman.availableMemory(), is( 8192L ) );
+        assertThat( mman.usedMemory() + mman.availableMemory(), is( 8192L ) );
+
+        mman.allocateAligned( 32 );
+        assertThat( mman.usedMemory(), is( greaterThanOrEqualTo( 32L ) ) );
+        assertThat( mman.availableMemory(), is( lessThanOrEqualTo( 8192L - 32 ) ) );
+        assertThat( mman.usedMemory() + mman.availableMemory(), is( 8192L ) );
+
+        mman.allocateAligned( 32 );
+        assertThat( mman.usedMemory(), is( greaterThanOrEqualTo( 64L ) ) );
+        assertThat( mman.availableMemory(), is( lessThanOrEqualTo( 8192L - 32 - 32 ) ) );
+        assertThat( mman.usedMemory() + mman.availableMemory(), is( 8192L ) );
+    }
 }
diff --git a/community/io/src/test/java/org/neo4j/io/pagecache/impl/muninn/PageListTest.java b/community/io/src/test/java/org/neo4j/io/pagecache/impl/muninn/PageListTest.java
@@ -1206,9 +1206,9 @@ public void addressesMustBeZeroBeforeInitialisation() throws Exception
     @Test
     public void initialisingBufferMustConsumeMemoryFromMemoryManager() throws Exception
     {
-        long initialUsedMemory = mman.sumUsedMemory();
+        long initialUsedMemory = mman.usedMemory();
         pageList.initBuffer( pageRef );
-        long resultingUsedMemory = mman.sumUsedMemory();
+        long resultingUsedMemory = mman.usedMemory();
         int allocatedMemory = (int) (resultingUsedMemory - initialUsedMemory);
         assertThat( allocatedMemory, greaterThanOrEqualTo( pageSize ) );
         assertThat( allocatedMemory, lessThanOrEqualTo( pageSize + ALIGNMENT ) );