Github user mridulm commented on a diff in the pull request:
https://github.com/apache/spark/pull/16603#discussion_r97846848
--- Diff: core/src/main/java/org/apache/spark/memory/TaskMemoryManager.java
---
@@ -144,23 +152,49 @@ public long acquireExecutionMemory(long required,
MemoryConsumer consumer) {
// spilling, avoid to have too many spilled files.
if (got < required) {
// Call spill() on other consumers to release memory
+ // Sort the consumers according their memory usage. So we avoid
spilling the same consumer
+ // which is just spilled in last few times and re-spilling on it
will produce many small
+ // spill files.
+ sortedConsumers.clear();
for (MemoryConsumer c: consumers) {
if (c != consumer && c.getUsed() > 0 && c.getMode() == mode) {
- try {
- long released = c.spill(required - got, consumer);
- if (released > 0) {
- logger.debug("Task {} released {} from {} for {}",
taskAttemptId,
- Utils.bytesToString(released), c, consumer);
- got += memoryManager.acquireExecutionMemory(required -
got, taskAttemptId, mode);
- if (got >= required) {
- break;
- }
+ Long key = c.getUsed();
+ // If there is existing consumer using the same amount of
memory,
+ // increasing the key.
+ while (sortedConsumers.containsKey(key)) {
+ key += 1;
+ }
+ sortedConsumers.put(key, c);
--- End diff --
Why are we fudging the key here ?
Either make the value a list of memory consumers or use a composite key
with a custom comparator : former is preferred.
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