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From "Nitsan Wakart (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-11853) Improve Cassandra-Stress latency measurement
Date Tue, 24 May 2016 00:53:12 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-11853?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15297454#comment-15297454
] 

Nitsan Wakart commented on CASSANDRA-11853:
-------------------------------------------

So, with 100K ops/sec you hit a 150ms STW pause. The pause makes 15K ops queue up, 30 per
thread. When the pause ends, all threads go as fast as they can to catch up. At this point
they are going as hard as throughput. If max throughput for the system is 200K per second,
the buildup alone will take 75ms to clear. Assuming some extra fallout from this and some
contention as 500 threads scramble I can see how the end result will be an observed 300ms
response time for one of them.

> Improve Cassandra-Stress latency measurement
> --------------------------------------------
>
>                 Key: CASSANDRA-11853
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11853
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Tools
>            Reporter: Nitsan Wakart
>            Assignee: Nitsan Wakart
>             Fix For: 3.x
>
>
> Currently CS reports latency using a sampling latency container and reporting service
time (as opposed to response time from intended schedule) leading to coordinated omission.
> Fixed here:
> https://github.com/nitsanw/cassandra/tree/co-correction



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