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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2945) stop using string for block name in LRU block cache/hfile
Date Wed, 01 Sep 2010 02:09:54 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2945?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12904873#action_12904873

Jonathan Gray commented on HBASE-2945:

Also, we should review the high/low watermark values.  I made those up rather arbitrarily.
 With the current defaults, what I've seen in practice is under heady read load there are
very frequent evictions (ever few seconds) but each is only evicting a small amount of memory
(10% of total block cache size).  Considering the evictions are non-blocking and do seem to
keep up regardless, would evicting 2-3X as much each time yield better or worse GC performance?
 Ideal behavior, performance/gc aside, I think would be to have as little evicted each time
as possible.

More discussion about changing the block cache lru is over on HBASE-2663.

> stop using string for block name in LRU block cache/hfile
> ---------------------------------------------------------
>                 Key: HBASE-2945
>                 URL: https://issues.apache.org/jira/browse/HBASE-2945
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.89.20100621
>            Reporter: ryan rawson
> all my profiling runs indicate there is a large number of string/char[] objects and string
manipulation is taking a long time in profiling runs.  These come from the LRU block cache,
block id.  Also we should support the eviction of blocks belonging to particular hfiles, and
the current code doesn't help with that right now.
> Let's do something better.  Whatever that might be.

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