Github user andrewor14 commented on a diff in the pull request:
https://github.com/apache/spark/pull/10170#discussion_r47028671
--- Diff:
core/src/main/scala/org/apache/spark/memory/StorageMemoryPool.scala ---
@@ -73,27 +73,31 @@ class StorageMemoryPool(lock: Object) extends
MemoryPool(lock) with Logging {
*
* @param blockId the ID of the block we are acquiring storage memory for
* @param numBytesToAcquire the size of this block
- * @param numBytesToFree the size of space to be freed through evicting
blocks
+ * @param maxNumBytesToFree the maximum amount of space to be freed
through evicting blocks
* @return whether all N bytes were successfully granted.
*/
def acquireMemory(
blockId: BlockId,
numBytesToAcquire: Long,
- numBytesToFree: Long,
+ maxNumBytesToFree: Long,
evictedBlocks: mutable.Buffer[(BlockId, BlockStatus)]): Boolean =
lock.synchronized {
assert(numBytesToAcquire >= 0)
- assert(numBytesToFree >= 0)
+ assert(maxNumBytesToFree >= 0)
assert(memoryUsed <= poolSize)
- memoryStore.ensureFreeSpace(blockId, numBytesToFree, evictedBlocks)
- // Register evicted blocks, if any, with the active task metrics
- Option(TaskContext.get()).foreach { tc =>
- val metrics = tc.taskMetrics()
- val lastUpdatedBlocks =
metrics.updatedBlocks.getOrElse(Seq[(BlockId, BlockStatus)]())
- metrics.updatedBlocks = Some(lastUpdatedBlocks ++
evictedBlocks.toSeq)
+ if (numBytesToAcquire > memoryFree && maxNumBytesToFree > 0) {
+ val additionalMemoryRequired = numBytesToAcquire - memoryFree
+ memoryStore.evictBlocksToFreeSpace(
--- End diff --
after looking at the test case I think we should add a check here to do
this only if there's a chance that evicting can free us enough memory, i.e.
```
val additionalMemoryRequired = math.max(0, numBytesToAcquire - memoryFree)
val numBytesToFree = math.min(maxNumBytesToFree, additionalMemoryRequired)
// Only evict blocks if there is a chance that doing so will grant us what
we want
if (numBytesToFree > 0 && numBytesToFree <= memoryUsed) {
memoryStore.evictBlocksToFreeSpace(...)
...
}
```
If we do this then we can't have the case where we try to free 150B from
evicting blocks when there are only 100B worth of blocks.
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