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From "Jason Brown (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1632) Thread workflow and cpu affinity
Date Thu, 21 Nov 2013 20:00:37 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1632?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13829280#comment-13829280
] 

Jason Brown commented on CASSANDRA-1632:
----------------------------------------

[~benedict]CASSANDRA-3005 is where the active/backlog queues were introduced. Can you elaborate
more on the race condition you think is there? I agree there may be one, esp. when the queues
get swapped (but I don't think there's a correctness problem with one, AFAICT).

However, Benedict is correct about getPendingMessages() needing to be fixed. Next rev coming
up shortly...

> Thread workflow and cpu affinity
> --------------------------------
>
>                 Key: CASSANDRA-1632
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1632
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Chris Goffinet
>            Assignee: Jason Brown
>              Labels: performance
>             Fix For: 2.1
>
>         Attachments: 1632-v2.txt, 1632-v3.diff, 1632_batchRead-v1.diff, threadAff_reads.txt,
threadAff_writes.txt
>
>
> Here are some thoughts I wanted to write down, we need to run some serious benchmarks
to see the benefits:
> 1) All thread pools for our stages use a shared queue per stage. For some stages we could
move to a model where each thread has its own queue. This would reduce lock contention on
the shared queue. This workload only suits the stages that have no variance, else you run
into thread starvation. Some stages that this might work: ROW-MUTATION.
> 2) Set cpu affinity for each thread in each stage. If we can pin threads to specific
cores, and control the workflow of a message from Thrift down to each stage, we should see
improvements on reducing L1 cache misses. We would need to build a JNI extension (to set cpu
affinity), as I could not find anywhere in JDK where it was exposed. 
> 3) Batching the delivery of requests across stage boundaries. Peter Schuller hasn't looked
deep enough yet into the JDK, but he thinks there may be significant improvements to be had
there. Especially in high-throughput situations. If on each consumption you were to consume
everything in the queue, rather than implying a synchronization point in between each request.



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