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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7796) Stop inheriting liveRatio/computedAt from previous memtables
Date Wed, 20 Aug 2014 01:40:20 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7796?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14103213#comment-14103213
] 

Benedict commented on CASSANDRA-7796:
-------------------------------------

Are you sure this is better? I think we should inherit the ratio, but not the last computed
at. This patch IMO makes it easier to OOM by inserts outpacing the liveRatio calculation after
memtable switch. With inheritance we are only at risk if the data shape changes; with this
patch we are at risk with the same data shape which to me seems like a larger affect window.

> Stop inheriting liveRatio/computedAt from previous memtables
> ------------------------------------------------------------
>
>                 Key: CASSANDRA-7796
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7796
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Aleksey Yeschenko
>            Assignee: Aleksey Yeschenko
>            Priority: Minor
>             Fix For: 2.0.10
>
>         Attachments: 7796.txt
>
>
> CASSANDRA-6945 helped to reduce the risk of calculating an outlier liveRatio value, and
having to stick with it for a long time, by making liveRatio per-memtable and not per-cf.
> The added optimization of inheriting liveRatio/calculatedAt to minimize recalculations,
however, took us a step back to before CASSANDRA-6945.
> I suggest we get rid of inheriting the old values altogether, but reduce the rate of
recalculation by demanding 10x increase in ops to trigger recalc, instead of the previous
2x.



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