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https://issues.apache.org/jira/browse/CASSANDRA-6746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13933665#comment-13933665
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Benedict commented on CASSANDRA-6746:
-------------------------------------
It seems like all of the discussion on the prior ticket CASSANDRA-1470 that
introduced it circles around how to implement it, and not on whether
implementing it is actually necessary. It seems to be taken as read that it is,
but I'm not totally convinced by that.
Either way, probably the best long term solution that would definitely work is
to perform the incremental replacement I previously suggested, as this would
allow us to DONTNEED the old sstables incrementally, thereby saving at minimum
as much memory churn as we can save optimally with this approach, and then
leave the new pages to the OS to decide what to do with. If they're not hot the
newly freed memory from the old tables should give plenty enough room for the
regular ageing algorithm to kick in and ensure they're selected for eviction in
preference to anything that is in use; it also bounds how much of the system
memory can churn, which is currently unbounded (although large tricklefsync
would achieve this also).
> Reads have a slow ramp up in speed
> ----------------------------------
>
> Key: CASSANDRA-6746
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6746
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Ryan McGuire
> Assignee: Benedict
> Labels: performance
> Fix For: 2.1 beta2
>
> Attachments: 2.1_vs_2.0_read.png, 6746-patched.png, 6746.txt,
> cassandra-2.0-bdplab-trial-fincore.tar.bz2,
> cassandra-2.1-bdplab-trial-fincore.tar.bz2
>
>
> On a physical four node cluister I am doing a big write and then a big read.
> The read takes a long time to ramp up to respectable speeds.
> !2.1_vs_2.0_read.png!
> [See data
> here|http://ryanmcguire.info/ds/graph/graph.html?stats=stats.2.1_vs_2.0_vs_1.2.retry1.json&metric=interval_op_rate&operation=stress-read&smoothing=1]
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