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https://issues.apache.org/jira/browse/CASSANDRA-7546?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14088738#comment-14088738
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graham sanderson commented on CASSANDRA-7546:
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I ran my smoke test on this and it is as expected; I have added the patch (with
a warn log statement on memtable flush if we have resorted to pessimistic
concurrency for some rows) to our 2.0.9 beta env... I will try and repro there
with a node down (though this cluster is pretty much limited by commit volumes
under high load, so can't equal production concurrency), but that said I just
want to check that everything is OK, before I patch a single node in production
(also 2.0.9)
On a separate note (I don't have access to a 2.1 cluster ATM), it would be
interesting to try something similar to
http://www.datastax.com/dev/blog/cassandra-2-1-now-over-50-faster
with a node down & hinting as a test case for this on 2.1
> AtomicSortedColumns.addAllWithSizeDelta has a spin loop that allocates memory
> -----------------------------------------------------------------------------
>
> Key: CASSANDRA-7546
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7546
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: graham sanderson
> Assignee: graham sanderson
> Attachments: 7546.20.txt, 7546.20_2.txt, 7546.20_3.txt,
> 7546.20_4.txt, 7546.20_5.txt, 7546.20_6.txt, 7546.20_7.txt, 7546.20_alt.txt,
> suggestion1.txt, suggestion1_21.txt
>
>
> In order to preserve atomicity, this code attempts to read, clone/update,
> then CAS the state of the partition.
> Under heavy contention for updating a single partition this can cause some
> fairly staggering memory growth (the more cores on your machine the worst it
> gets).
> Whilst many usage patterns don't do highly concurrent updates to the same
> partition, hinting today, does, and in this case wild (order(s) of magnitude
> more than expected) memory allocation rates can be seen (especially when the
> updates being hinted are small updates to different partitions which can
> happen very fast on their own) - see CASSANDRA-7545
> It would be best to eliminate/reduce/limit the spinning memory allocation
> whilst not slowing down the very common un-contended case.
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