[jira] [Commented] (MESOS-2103) Expose number of processes and threads in a container

["Chi Zhang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MESOS-2103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14325303#comment-14325303 ] 

Chi Zhang commented on MESOS-2103:
----------------------------------

Per discussion with [~idownes], limit the scope of this ticket to only expose the number of pids and tids in a container, which helps understand the total cpu throttling time issue in the description. 

A better method is needed for MESOS-2365 (reading from the /proc isn't atomic for all the threads, which makes it very inaccurate to say the least). 

> Expose number of processes and threads in a container
> -----------------------------------------------------
>
>                 Key: MESOS-2103
>                 URL: https://issues.apache.org/jira/browse/MESOS-2103
>             Project: Mesos
>          Issue Type: Improvement
>          Components: isolation
>    Affects Versions: 0.20.0
>            Reporter: Ian Downes
>            Assignee: Chi Zhang
>              Labels: twitter
>
> The CFS cpu statistics (cpus_nr_throttled, cpus_nr_periods, cpus_throttled_time) are difficult to interpret.
> 1) nr_throttled is the number of intervals where *any* throttling occurred
> 2) throttled_time is the aggregate time *across all runnable tasks* (tasks in the Linux sense).
> For example, in a typical 60 second sampling interval: nr_periods = 600, nr_throttled could be 60, i.e., 10% of intervals, but throttled_time could be much higher than (60/600) * 60 = 6 seconds if there is more than one task that is runnable but throttled. *Each* throttled task contributes to the total throttled time.
> Small test to demonstrate throttled_time > nr_periods * quota_interval:
> 5 x {{'openssl speed'}} running with quota=100ms:
> {noformat}
> cat cpu.stat && sleep 1 && cat cpu.stat
> nr_periods 3228
> nr_throttled 1276
> throttled_time 528843772540
> nr_periods 3238
> nr_throttled 1286
> throttled_time 531668964667
> {noformat}
> All 10 intervals throttled (100%) for total time of 2.8 seconds in 1 second ("more than 100%" of the time interval)
> It would be helpful to expose the number and state of tasks in the container cgroup. This would be at a very coarse granularity but would give some guidance.



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