srowen commented on a change in pull request #34846:
URL: https://github.com/apache/spark/pull/34846#discussion_r767166912
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File path: core/src/main/scala/org/apache/spark/memory/MemoryManager.scala
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@@ -255,7 +256,15 @@ 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 (conf.get(MEMORY_ONHEAP_PAGESIZE_OPTIMIZE_ENABLED) &&
+ tungstenMemoryMode == MemoryMode.ON_HEAP &&
+ sizeAsBytes % (1024 * 1024) == 0 &&
+ Utils.isHumongousAllocation(sizeAsBytes)) {
+ sizeAsBytes - Platform.LONG_ARRAY_OFFSET
Review comment:
Yes. I think the current logic is good, just wondering if it matter much
if we do it in all cases. Maybe it's bad for small allocations, but is the
offset ever significant relative to the allocation size I wonder? probably not.
I wonder if there are future cases, different GCs, that we're not checking here
that also need this treatment
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