Examples of com.netflix.zeno.util.collections.heapfriendly.HeapFriendlyMapArrayRecycler

com.netflix.zeno.util.collections.heapfriendly.HeapFriendlyMapArrayRecycler

Contains two pools of Object[] arrays.

When Netflix's Video Metadata Service receives a FastBlob delta update, it applies the delta to it's FastBlobStateEngine, then indexes many Objects by their primary keys in hash tables.

Because ParNew is a stop the world event, and ParNew time is directly proportional to the number of Objects which survive after creation and must be copied to survivor spaces / OldGen, we can reduce the GC impact of Map creation if we reuse Objects which have already been promoted to OldGen.

We maintain two pools of Object[] arrays. One is for the "current" cycle, and one is for the "next" cycle. On each cycle, we take the Object arrays comprising the current HeapFriendlyHashMap segmented arrays, and return them to the "next" cycle pool. When we create new HeapFriendlyHashMap objects, we construct the segmented arrays with segments from the "current" cycle pool.

At the beginning of each update cycle, we swap the pointers to the "current" and "next" cycle pools. This way, we're always overwriting the data from 2 cycles ago, and the Object arrays just remain in OldGen. @author dkoszewnik

        }
    }


    @Test
    public void recyclesObjectArraysFromAlternatingCycles() throws Exception {
        HeapFriendlyMapArrayRecycler recycler = HeapFriendlyMapArrayRecycler.get();


        HeapFriendlyDerivableKeyHashMap<String, Integer> map = getMap(100);
        Object[] firstSegment = getFirstSegment(map);


        recycler.swapCycleObjectArrays();


        map.releaseObjectArrays();
        recycler.clearNextCycleObjectArrays();
        map = getMap(100);
        Object[] differentFirstSegment = getFirstSegment(map);


        Assert.assertNotSame(firstSegment, differentFirstSegment);


        recycler.swapCycleObjectArrays();


        map.releaseObjectArrays();
        recycler.clearNextCycleObjectArrays();
        map = getMap(100);
        Object[] firstSegmentAgain = getFirstSegment(map);


        Assert.assertSame(firstSegment, firstSegmentAgain);
    }

Examples of com.netflix.zeno.util.collections.heapfriendly.HeapFriendlyMapArrayRecycler

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