[jira] [Commented] (CASSANDRA-4032) memtable.updateLiveRatio() is blocking, causing insane latencies for writes

["Sylvain Lebresne (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-4032?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13250746#comment-13250746 ] 

Sylvain Lebresne commented on CASSANDRA-4032:
---------------------------------------------

Wouldn't using a ConcurrentSkipListSet simply the code? Feels like a lot of boilerplate to record that there is already a metering running (it's not like this is a hot path enough to justify the NBHM). 
                
> memtable.updateLiveRatio() is blocking, causing insane latencies for writes
> ---------------------------------------------------------------------------
>
>                 Key: CASSANDRA-4032
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4032
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Peter Schuller
>            Assignee: Peter Schuller
>             Fix For: 1.1.0
>
>         Attachments: 4032-v3.txt, CASSANDRA-4032-1.1.0-v1.txt, CASSANDRA-4032-1.1.0-v2.txt
>
>
> Reproduce by just starting a fresh cassandra with a heap large enough for live ratio calculation (which is {{O(n)}}) to be insanely slow, and then running {{./bin/stress -d host -n100000000 -t10}}. With a large enough heap and default flushing behavior this is bad enough that stress gets timeouts.
> Example ("blocked for" is my debug log added around submit()):
> {code}
>  INFO [MemoryMeter:1] 2012-03-09 15:07:30,857 Memtable.java (line 198) CFS(Keyspace='Keyspace1', ColumnFamily='Standard1') liveRatio is 8.89014894083727 (just-counted was 8.89014894083727).  calculation took 28273ms for 1320245 columns
>  WARN [MutationStage:8] 2012-03-09 15:07:30,857 Memtable.java (line 209) submit() blocked for: 231135
> {code}
> The calling code was written assuming a RejectedExecutionException is thrown, but it's not because {{DebuggableThreadPoolExecutor}} installs a blocking rejection handler.

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