hbase-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13082) Coarsen StoreScanner locks to RegionScanner
Date Fri, 16 Oct 2015 16:24:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13082?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14960961#comment-14960961
] 

stack commented on HBASE-13082:
-------------------------------

This is an important fix. I started to look at the rb and then got lost on why we were doing
certain things. I started to read over the issue but the issue has been going on for a long
time with us flip/flopping over whether this a good idea or not, lists of why this issue is
good and then downsides, and then stuff like the scan implementation changed while this issue
was going on. I think a one-pager is in order so can see in one place current approach, upsides
and downsides.... and that we have this before we do the code (or at least, it looks like
with this last patch, that we are trying an experiment -- which is sweet... lets factor the
findings back into the one-pager). With a one-pager, we'll be able to do a better review.
Thanks.

> Coarsen StoreScanner locks to RegionScanner
> -------------------------------------------
>
>                 Key: HBASE-13082
>                 URL: https://issues.apache.org/jira/browse/HBASE-13082
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: ramkrishna.s.vasudevan
>         Attachments: 13082-test.txt, 13082-v2.txt, 13082-v3.txt, 13082-v4.txt, 13082.txt,
13082.txt, HBASE-13082_1_WIP.patch, HBASE-13082_2_WIP.patch, HBASE-13082_3.patch, HBASE-13082_4.patch,
gc.png, gc.png, gc.png, hits.png, next.png, next.png
>
>
> Continuing where HBASE-10015 left of.
> We can avoid locking (and memory fencing) inside StoreScanner by deferring to the lock
already held by the RegionScanner.
> In tests this shows quite a scan improvement and reduced CPU (the fences make the cores
wait for memory fetches).
> There are some drawbacks too:
> * All calls to RegionScanner need to be remain synchronized
> * Implementors of coprocessors need to be diligent in following the locking contract.
For example Phoenix does not lock RegionScanner.nextRaw() and required in the documentation
(not picking on Phoenix, this one is my fault as I told them it's OK)
> * possible starving of flushes and compaction with heavy read load. RegionScanner operations
would keep getting the locks and the flushes/compactions would not be able finalize the set
of files.
> I'll have a patch soon.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message