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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7217) Native transport performance (with cassandra-stress) drops precipitously past around 1000 threads
Date Thu, 12 Nov 2015 23:34:11 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7217?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15003199#comment-15003199
] 

Ariel Weisberg commented on CASSANDRA-7217:
-------------------------------------------

My takeaway from the counters is that with 2000 threads working through 19 million writes
took more instructions, almost double the number of cache references,  more than double the
number of context switches, and double the number of dcache misses. So there was a big drop
in efficiency that could explain how this occurs even without contention or starvation.

Now if there is a way to have 2000 threads do this work more efficiently is a good question.
There are a lot more performance counters that might give insight into what having more threads
changed as well as profiling. I'll look into it tomorrow.

> Native transport performance (with cassandra-stress) drops precipitously past around
1000 threads
> -------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-7217
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7217
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Benedict
>            Assignee: Ariel Weisberg
>              Labels: performance, stress, triaged
>             Fix For: 3.1
>
>
> This is obviously bad. Let's figure out why it's happening and put a stop to it.



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