[jira] [Comment Edited] (CASSANDRA-8341) Expose time spent in each thread pool

["Robert Stupp (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-8341?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14219174#comment-14219174 ] 

Robert Stupp edited comment on CASSANDRA-8341 at 11/20/14 11:04 AM:
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Yea - that {{TheadMXBean.getCurrentThread...()}} hopefully directly accesses the CPU registers for that.
Not sure about that since the implementations are very OS specific (in {{hotspot/os/\*/vm/os_\*.cpp}} in OpenJDK source) and as such also specific to the CPU model.
If all the implementations access the CPU registers for that, it definitely better than {{System.nanoTime()}, which is consistent over CPU codes (-> NUMA - expensive).
Note: I don't want to make this ticket more complicated as necessary - just want to mention that metrics have their own overhead and should be used with care in sensitive areas like thread scheduling.


was (Author: snazy):
Yea - that {{TheadMXBean.getCurrentThread...()}} hopefully directly accesses the CPU registers for that.
Not sure about that since the implementations are very OS specific (in {{hotspot/os/*/vm/os_*.cpp}} in OpenJDK source) and as such also specific to the CPU model.
If all the implementations access the CPU registers for that, it definitely better than {{System.nanoTime()}, which is consistent over CPU codes (-> NUMA - expensive).
Note: I don't want to make this ticket more complicated as necessary - just want to mention that metrics have their own overhead and should be used with care in sensitive areas like thread scheduling.

> Expose time spent in each thread pool
> -------------------------------------
>
>                 Key: CASSANDRA-8341
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8341
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Chris Lohfink
>            Priority: Minor
>              Labels: metrics
>         Attachments: 8341.patch, 8341v2.txt
>
>
> Can increment a counter with time spent in each queue.  This can provide context on how much time is spent percentage wise in each stage.  Additionally can be used with littles law in future if ever want to try to tune the size of the pools.



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