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From "Jay Patel (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7882) Memtable slab allocation should scale logarithmically to improve occupancy rate
Date Fri, 10 Oct 2014 05:46:34 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14166426#comment-14166426
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Jay Patel commented on CASSANDRA-7882:
--------------------------------------

[~benedict], we've done initial testing with 3K tables, running for a day & looks good
so far. 

Should we keep the start region size configurable, instead of hard-coded 8kb? This will allow
fine tuning specific use case, for instance - If payload is always around 400 to 500kb, user
can have start size as 512kb instead of scaling from 8kb. Actually, we've one use case like
that.

Let me know your thoughts or I'll submit a final patch with the todos completed.


> Memtable slab allocation should scale logarithmically to improve occupancy rate
> -------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-7882
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7882
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Jay Patel
>            Assignee: Jay Patel
>              Labels: performance
>             Fix For: 2.1.1
>
>         Attachments: trunk-7882.txt
>
>
> CASSANDRA-5935 allows option to disable region-based allocation for on-heap memtables
but there is no option to disable it for off-heap memtables (memtable_allocation_type: offheap_objects).

> Disabling region-based allocation will allow us to pack more tables in the schema since
minimum of 1MB region won't be allocated per table. Downside can be more fragmentation which
should be controllable by using better allocator like JEMalloc.
> How about below option in yaml?:
> memtable_allocation_type: unslabbed_offheap_objects
> Thanks.



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