Github user andrewor14 commented on a diff in the pull request:
https://github.com/apache/spark/pull/11874#discussion_r57253712
--- Diff:
core/src/main/scala/org/apache/spark/memory/StorageMemoryPool.scala ---
@@ -56,12 +58,30 @@ private[memory] class StorageMemoryPool(lock: Object)
extends MemoryPool(lock) w
/**
* Acquire N bytes of memory to cache the given block, evicting existing
ones if necessary.
- *
+ *
* @return whether all N bytes were successfully granted.
*/
- def acquireMemory(blockId: BlockId, numBytes: Long): Boolean =
lock.synchronized {
- val numBytesToFree = math.max(0, numBytes - memoryFree)
- acquireMemory(blockId, numBytes, numBytesToFree)
+ def acquireMemory(blockId: BlockId, numBytes: Long): Boolean = {
+ // First, attempt to acquire as much memory as we can without
performing any eviction
--- End diff --
I would expand on this: "Otherwise, another thread may jump in and use up
some free memory as soon as we release the lock, in which case we may evict too
few blocks to store this block later."
Right now it's not clear why we need to do this in 2 steps.
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