mehakmeet commented on code in PR #5754:
URL: https://github.com/apache/hadoop/pull/5754#discussion_r1240673021
##########
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:
Okay, but when we are adding the node to the head, doesn't it make more
sense to check if the current node is tail, get the previous of this, and set
that to tail? This would work, was just interested if we can avoid traversing
the list 🤔
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