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https://issues.apache.org/jira/browse/CASSANDRA-7546?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14123920#comment-14123920
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graham sanderson commented on CASSANDRA-7546:
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Yes, I'm actually waiting on one of our main Cassandra Ops guys to come back
from vacation on Monday to upgrade one of our clusters to 2.1 before I can run
the stress tests, but we do have the patch running in production on 2.0.x.
It detects hints, and it would also seem (which makes sense) fast hint playback
of things with low cardinality keys
I will certainly change the log level to INFO or DEBUG though... as this
shouldn't really be a WARNING.
> 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
> Fix For: 2.1.1
>
> 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_7b.txt,
> 7546.20_alt.txt, 7546.20_async.txt, 7546.21_v1.txt, hint_spikes.png,
> suggestion1.txt, suggestion1_21.txt, young_gen_gc.png
>
>
> 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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