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From "Lars Hofhansl (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4752) Don't create an unnecessary LinkedList when evicting from the BlockCache
Date Sun, 06 Nov 2011 16:44:52 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13145039#comment-13145039
] 

Lars Hofhansl commented on HBASE-4752:
--------------------------------------

One part that is still different in the old implementation LruBlockCache.free() always drained
the entire queue. Now we only drain until we have evicted enough.
Not sure whether that was intentional or not, but to be functionally equivalent we should
do this:
{code}
while(...) {
...
  if (freedBytes >= toFree) {
    queue.clear();
    return freedBytes;
  }
}
queue.clear();
...
{code}

Or similar (or clear() in a finally block).

                
> Don't create an unnecessary LinkedList when evicting from the BlockCache
> ------------------------------------------------------------------------
>
>                 Key: HBASE-4752
>                 URL: https://issues.apache.org/jira/browse/HBASE-4752
>             Project: HBase
>          Issue Type: Improvement
>          Components: performance, regionserver
>    Affects Versions: 0.90.4
>            Reporter: Benoit Sigoure
>            Assignee: Ted Yu
>            Priority: Minor
>             Fix For: 0.94.0
>
>         Attachments: 0001-HBASE-4752-Don-t-create-an-unnecessary-LinkedList-wh.patch,
4752-trunk-v2.txt, 4752-trunk.txt
>
>
> When evicting from the BlockCache, the code creates a LinkedList containing every single
block sorted by access time.  This list is created from a PriorityQueue.  I don't believe
it is necessary, as the PriorityQueue can be used directly.

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