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src/hotspot/share/gc/shenandoah/shenandoahMemoryPool.cpp

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rev 53841 : 8219524: Shenandoah misreports "committed" size in MemoryMXBean
Reviewed-by: XXX

*** 24,46 **** #include "precompiled.hpp" #include "gc/shenandoah/shenandoahMemoryPool.hpp" ShenandoahMemoryPool::ShenandoahMemoryPool(ShenandoahHeap* heap) : CollectedMemoryPool("Shenandoah", ! heap->capacity(), heap->max_capacity(), true /* support_usage_threshold */), _heap(heap) {} MemoryUsage ShenandoahMemoryPool::get_memory_usage() { size_t initial = initial_size(); size_t max = max_size(); size_t used = used_in_bytes(); size_t committed = _heap->committed(); assert(initial <= max, "initial: " SIZE_FORMAT ", max: " SIZE_FORMAT, initial, max); assert(used <= max, "used: " SIZE_FORMAT ", max: " SIZE_FORMAT, used, max); assert(committed <= max, "committed: " SIZE_FORMAT ", max: " SIZE_FORMAT, committed, max); assert(used <= committed, "used: " SIZE_FORMAT ", committed: " SIZE_FORMAT, used, committed); return MemoryUsage(initial, used, committed, max); } --- 24,52 ---- #include "precompiled.hpp" #include "gc/shenandoah/shenandoahMemoryPool.hpp" ShenandoahMemoryPool::ShenandoahMemoryPool(ShenandoahHeap* heap) : CollectedMemoryPool("Shenandoah", ! heap->initial_capacity(), heap->max_capacity(), true /* support_usage_threshold */), _heap(heap) {} MemoryUsage ShenandoahMemoryPool::get_memory_usage() { size_t initial = initial_size(); size_t max = max_size(); size_t used = used_in_bytes(); size_t committed = _heap->committed(); + // These asserts can never fail: max is stable, and all updates to other values never overflow max. assert(initial <= max, "initial: " SIZE_FORMAT ", max: " SIZE_FORMAT, initial, max); assert(used <= max, "used: " SIZE_FORMAT ", max: " SIZE_FORMAT, used, max); assert(committed <= max, "committed: " SIZE_FORMAT ", max: " SIZE_FORMAT, committed, max); + + // Committed and used are updated concurrently and independently. They can momentarily break + // the assert below, which would also fail in downstream code. To avoid that, adjust values + // to make sense under the race. See JDK-8207200. + committed = MAX2(used, committed); assert(used <= committed, "used: " SIZE_FORMAT ", committed: " SIZE_FORMAT, used, committed); return MemoryUsage(initial, used, committed, max); }
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