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Posted to reviews@spark.apache.org by GitBox <gi...@apache.org> on 2021/12/15 14:53:04 UTC
[GitHub] [spark] WangGuangxin commented on a change in pull request #34846: [SPARK-37593][CORE] Optimize HeapMemoryAllocator to avoid memory waste when using G1GC
WangGuangxin commented on a change in pull request #34846:
URL: https://github.com/apache/spark/pull/34846#discussion_r769700852
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File path: core/src/main/scala/org/apache/spark/memory/MemoryManager.scala
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@@ -255,7 +256,17 @@ private[spark] abstract class MemoryManager(
}
val size = ByteArrayMethods.nextPowerOf2(maxTungstenMemory / cores / safetyFactor)
val default = math.min(maxPageSize, math.max(minPageSize, size))
- conf.get(BUFFER_PAGESIZE).getOrElse(default)
+ val sizeAsBytes = conf.get(BUFFER_PAGESIZE).getOrElse(default)
+ // If we are using G1 GC, it's better to take the LONG_ARRAY_OFFSET into consideration
+ // so that the requested memory size is power of 2 and can be divided by G1 region size
+ // to reduce memory waste within one G1 region
+ if (Utils.isG1GarbageCollector &&
+ tungstenMemoryMode == MemoryMode.ON_HEAP &&
+ sizeAsBytes % (1024 * 1024) == 0) {
+ sizeAsBytes - Platform.LONG_ARRAY_OFFSET
Review comment:
I see what you mean, you are right
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