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From "Stefania (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8897) Remove FileCacheService, instead pooling the buffers
Date Thu, 14 May 2015 08:05:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8897?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14543355#comment-14543355
] 

Stefania commented on CASSANDRA-8897:
-------------------------------------

[~benedict], this is ready for review. 

Since my last comment I fixed a few bugs but did not change anything substantial.

There was indeed a performance degradation when reading the data generated with the stress
profile of CASSANDRA-9240. It was about 600 ops/second slower on my machine (see 9240_test_results.txt
attached) and about 1000 ops/second slower on cstar_perf (albeit without a restart).

I compared two VisualVM sampler snapshots (attached) and nailed it down to the screenshot
also attached. I then changed Ref.GlobalState to use a concurrent hash set rather than a concurrent
linked queue and the degradation disappeared.

I've also run several cstar_perf tests, with or without the CASSANDRA-9240 profile, with different
number of entries and threads. Here are some of them:

http://cstar.datastax.com/tests/id/26987156-fa0c-11e4-94a5-42010af0688f
http://cstar.datastax.com/tests/id/1915bc2a-fa05-11e4-9b87-42010af0688f
http://cstar.datastax.com/tests/id/f7a00bf4-fa09-11e4-9b87-42010af0688f

(the diagrams have some problems and occasionally are missing, not sure why)

And here are the Jenkins results, which look identical to trunk:

http://cassci.datastax.com/view/Dev/view/stef1927/job/stef1927-8897-testall/lastCompletedBuild/testReport/
http://cassci.datastax.com/view/Dev/view/stef1927/job/stef1927-8897-dtest/lastCompletedBuild/testReport/


> Remove FileCacheService, instead pooling the buffers
> ----------------------------------------------------
>
>                 Key: CASSANDRA-8897
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8897
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Assignee: Stefania
>             Fix For: 3.x
>
>         Attachments: 9240_test_results.txt, snapshot-1431582436640-cpu-backtraces.png,
snapshot-1431582436640-cpu-calltree-compression-8897.nps, snapshot-1431582436640-cpu-calltree-compression-trunk.nps
>
>
> After CASSANDRA-8893, a RAR will be a very lightweight object and will not need caching,
so we can eliminate this cache entirely. Instead we should have a pool of buffers that are
page-aligned.



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