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Re: [PATCH] softirq: let ksoftirqd do its job

From Jesper Dangaard Brouer <brouer@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH] softirq: let ksoftirqd do its job
Date 2016-09-01 15:40 +0200
Message-ID <scAnM-2te-19@gated-at.bofh.it> (permalink)
References (6 earlier) <scy2B-11X-5@gated-at.bofh.it> <scyP0-1lf-29@gated-at.bofh.it> <sczrI-1Sc-25@gated-at.bofh.it> <sczrI-1Sc-27@gated-at.bofh.it> <sczBo-1Vn-15@gated-at.bofh.it>
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On Thu, 1 Sep 2016 14:48:39 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> On Thu, Sep 01, 2016 at 02:38:59PM +0200, Jesper Dangaard Brouer wrote:
> > On Thu, 1 Sep 2016 14:29:25 +0200
> > Jesper Dangaard Brouer <brouer@redhat.com> wrote:
> >   
> > > On Thu, 1 Sep 2016 13:53:56 +0200
> > > Peter Zijlstra <peterz@infradead.org> wrote:
> > >   
> > > > On Thu, Sep 01, 2016 at 01:02:31PM +0200, Jesper Dangaard Brouer wrote:    
> > > > >    PID  S  %CPU     TIME+  COMMAND
> > > > >      3  R  50.0  29:02.23  ksoftirqd/0
> > > > >  10881  R  10.7   1:01.61  udp_sink
> > > > >  10837  R  10.0   1:05.20  udp_sink
> > > > >  10852  S  10.0   1:01.78  udp_sink
> > > > >  10862  R  10.0   1:05.19  udp_sink
> > > > >  10844  S   9.7   1:01.91  udp_sink
> > > > > 
> > > > > This is strange, why is ksoftirqd/0 getting 50% of the CPU time???      
> > > > 
> > > > Do you run your udp_sink thingy in a cpu-cgroup?    
> > > 
> > > That was also Paolo's feedback (IRC).  I'm not aware of it, but it
> > > might be some distribution (Fedora 22) default thing.  
> > 
> > Correction, on the server-under-test, I'm actually running RHEL7.2
> > 
> >   
> > > How do I verify/check if I have enabled a cpu-cgroup?  
> > 
> > Hannes says I can look in "/proc/self/cgroup"
> > 
> >  $ cat /proc/self/cgroup
> >  7:net_cls:/
> >  6:blkio:/
> >  5:devices:/
> >  4:perf_event:/
> >  3:cpu,cpuacct:/
> >  2:cpuset:/
> >  1:name=systemd:/user.slice/user-1000.slice/session-c1.scope
> >  
> > And that "/" indicate I've not enabled cgroups, right?  
> 
> Mostly so. I think RHEL/Fedora has SCHED_AUTOGROUP enabled, and you can
> find that through:
> 
> cat /proc/self/autogroup

$ cat /proc/self/autogroup
/autogroup-88 nice 0

> And disable with the noautogroup boot param, or:
> 
> echo 0 > /proc/sys/kernel/sched_autogroup_enabled

Looks like it is enabled on my system:

$ grep -H . /proc/sys/kernel/sched_autogroup_enabled
/proc/sys/kernel/sched_autogroup_enabled:1


> although this latter will leave the current state intact while avoiding
> creation of any further autogroups iirc.

$ sudo sh -c 'echo 0 > /proc/sys/kernel/sched_autogroup_enabled'
$ grep -H . /proc/sys/kernel/sched_autogroup_enabled
/proc/sys/kernel/sched_autogroup_enabled:0

$ sudo systemctl restart sshd

Starting new SSH login:

$ cat /proc/self/autogroup
/autogroup-153 nice 0

Hmmm, still enabled...

$ sudo systemctl stop sshd
$ sudo systemctl start sshd
$ grep -H . /proc/sys/kernel/sched_autogroup_enabled
/proc/sys/kernel/sched_autogroup_enabled:0
$ cat /proc/self/autogroup
/autogroup-158 nice 0

Still... enabled!
Hmmm.. more idea how to disable this???

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer

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Thread

[PATCH] softirq: let ksoftirqd do its job Eric Dumazet <eric.dumazet@gmail.com> - 2016-08-31 19:50 +0200
  Re: [PATCH] softirq: let ksoftirqd do its job Jesper Dangaard Brouer <jbrouer@redhat.com> - 2016-08-31 21:50 +0200
    Re: [PATCH] softirq: let ksoftirqd do its job Eric Dumazet <eric.dumazet@gmail.com> - 2016-08-31 22:50 +0200
      Re: [PATCH] softirq: let ksoftirqd do its job Jesper Dangaard Brouer <jbrouer@redhat.com> - 2016-09-01 00:00 +0200
        Re: [PATCH] softirq: let ksoftirqd do its job Eric Dumazet <eric.dumazet@gmail.com> - 2016-09-01 00:30 +0200
          Re: [PATCH] softirq: let ksoftirqd do its job Rick Jones <rick.jones2@hpe.com> - 2016-09-01 00:50 +0200
            Re: [PATCH] softirq: let ksoftirqd do its job Eric Dumazet <eric.dumazet@gmail.com> - 2016-09-01 01:20 +0200
              Re: [PATCH] softirq: let ksoftirqd do its job Rick Jones <rick.jones2@hpe.com> - 2016-09-01 01:40 +0200
                Re: [PATCH] softirq: let ksoftirqd do its job Jesper Dangaard Brouer <brouer@redhat.com> - 2016-09-01 12:40 +0200
                Re: [PATCH] softirq: let ksoftirqd do its job Eric Dumazet <eric.dumazet@gmail.com> - 2016-09-01 15:10 +0200
        Re: [PATCH] softirq: let ksoftirqd do its job Jesper Dangaard Brouer <brouer@redhat.com> - 2016-09-01 13:10 +0200
          Re: [PATCH] softirq: let ksoftirqd do its job Hannes Frederic Sowa <hannes@redhat.com> - 2016-09-01 13:20 +0200
          Re: [PATCH] softirq: let ksoftirqd do its job Peter Zijlstra <peterz@infradead.org> - 2016-09-01 14:00 +0200
            Re: [PATCH] softirq: let ksoftirqd do its job Jesper Dangaard Brouer <brouer@redhat.com> - 2016-09-01 14:40 +0200
              Re: [PATCH] softirq: let ksoftirqd do its job Jesper Dangaard Brouer <brouer@redhat.com> - 2016-09-01 14:40 +0200
                Re: [PATCH] softirq: let ksoftirqd do its job Peter Zijlstra <peterz@infradead.org> - 2016-09-01 14:50 +0200
                Re: [PATCH] softirq: let ksoftirqd do its job Jesper Dangaard Brouer <brouer@redhat.com> - 2016-09-01 15:40 +0200
                Re: [PATCH] softirq: let ksoftirqd do its job Peter Zijlstra <peterz@infradead.org> - 2016-09-01 17:30 +0200
                Re: [PATCH] softirq: let ksoftirqd do its job Jesper Dangaard Brouer <brouer@redhat.com> - 2016-09-02 10:40 +0200
                Re: [PATCH] softirq: let ksoftirqd do its job Eric Dumazet <eric.dumazet@gmail.com> - 2016-09-01 15:10 +0200
                Re: [PATCH] softirq: let ksoftirqd do its job Hannes Frederic Sowa <hannes@redhat.com> - 2016-09-01 15:10 +0200
                Re: [PATCH] softirq: let ksoftirqd do its job Eric Dumazet <eric.dumazet@gmail.com> - 2016-09-01 15:30 +0200
      Re: [PATCH] softirq: let ksoftirqd do its job Hannes Frederic Sowa <hannes@redhat.com> - 2016-09-01 14:10 +0200
        Re: [PATCH] softirq: let ksoftirqd do its job Eric Dumazet <eric.dumazet@gmail.com> - 2016-09-01 15:00 +0200
  Re: [PATCH] softirq: let ksoftirqd do its job Hannes Frederic Sowa <hannes@redhat.com> - 2016-09-01 14:10 +0200
  Re: [PATCH] softirq: let ksoftirqd do its job David Miller <davem@davemloft.net> - 2016-09-02 08:40 +0200

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