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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11323) BucketCache all the time!
Date Fri, 13 Jun 2014 23:00:06 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11323?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14031305#comment-14031305
] 

stack commented on HBASE-11323:
-------------------------------

[~enis] That is correct sir

> BucketCache all the time!
> -------------------------
>
>                 Key: HBASE-11323
>                 URL: https://issues.apache.org/jira/browse/HBASE-11323
>             Project: HBase
>          Issue Type: Sub-task
>          Components: io
>            Reporter: stack
>             Fix For: 0.99.0
>
>         Attachments: ReportBlockCache.pdf
>
>
> One way to realize the parent issue is to just enable bucket cache all the time; i.e.
always have offheap enabled.  Would have to do some work to make it drop-dead simple on initial
setup (I think it doable).
> So, upside would be the offheap upsides (less GC, less likely to go away and never come
back because of full GC when heap is large, etc.).
> Downside is higher latency.   In Nick's BlockCache 101 there is little to no difference
between onheap and offheap.  In a basic compare doing scans and gets -- details to follow
-- I have BucketCache deploy about 20% less ops than LRUBC when all incache and maybe 10%
less ops when falling out of cache.   I can't tell difference in means and 95th and 99th are
roughly same (more stable with BucketCache).  GC profile is much better with BucketCache --
way less.  BucketCache uses about 7% more user CPU.
> More detail on comparison to follow.
> I think the numbers disagree enough we should probably do the [~lhofhansl] suggestion,
that we allow you to have a table sit in LRUBC, something the current bucket cache layout
does not do.



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