[jira] [Commented] (HBASE-11323) BucketCache all the time!

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-11323?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14027349#comment-14027349 ] 

Lars Hofhansl commented on HBASE-11323:
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bq. I think the numbers disagree enough we should probably do the Lars Hofhansl suggestion, that we allow you to have a table sit in LRUBC, something the current bucket cache layout does not do.

How is that to do after you spent some time with it. When I looked last (didn't spend a lot of time, though), it did not look entirely trivial.

> 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
>
>
> 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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