virajjasani commented on code in PR #5754:
URL: https://github.com/apache/hadoop/pull/5754#discussion_r1247476231
##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/SingleFilePerBlockCache.java:
##########
@@ -247,9 +305,46 @@ private Entry getEntry(int blockNumber) {
throw new IllegalStateException(String.format("block %d not found in
cache", blockNumber));
}
numGets++;
+ addToHeadOfLinkedList(entry);
return entry;
}
+ /**
+ * Add the given entry to the head of the linked list.
+ *
+ * @param entry Block entry to add.
+ */
+ private void addToHeadOfLinkedList(Entry entry) {
+ blocksLock.writeLock().lock();
+ try {
+ if (head == null) {
+ head = entry;
+ tail = entry;
+ }
+ if (entry != head) {
+ Entry prev = entry.getPrevious();
+ Entry nxt = entry.getNext();
+ if (prev != null) {
+ prev.setNext(nxt);
+ }
+ if (nxt != null) {
+ nxt.setPrevious(prev);
+ }
+ entry.setPrevious(null);
+ entry.setNext(head);
+ head.setPrevious(entry);
+ head = entry;
+ }
+ if (tail != null) {
+ while (tail.getNext() != null) {
+ tail = tail.getNext();
+ }
+ }
Review Comment:
nice idea, it might be more beneficial for UT to test this.
i am also planning to refactor Entry class on it's own new class rather than
as an inner class of SingleFilePerBlockCache as part of next follow-up
sub-task. once we do that, then it might be even more easier to write some UT
to directly access head, tail pointers.
sorry, i was thinking this as sub-task so maybe adding UT can also be done
with sub-task. does that sound good?
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