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Re: [RFC PATCH 0/4] cgroup aware workqueues

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Hi Bandan,

> From: Bandan Das <bsd@redhat.com>
> 
> At Linuxcon last year, based on our presentation "vhost: sharing is 
better" [1],
> we had briefly discussed the idea of cgroup aware workqueues with Tejun. 
The
> following patches are a result of the discussion. They are in no way 
complete in
> that the changes are for unbounded workqueues only, but I just wanted to 
present my
> unfinished work as RFC and get some feedback.
> 
> 1/4 and 3/4 are simple cgroup changes and add a helper function.
> 2/4 is the main implementation.
> 4/4 changes vhost to use workqueues with support for cgroups.
>
> Example:
> vhost creates a worker thread when invoked for a kvm guest. Since,
> the guest is a normal process, the kernel thread servicing it should be
> attached to the vm process' cgroups.

I did some performance evaluation of different threading models in vhost, 
and in most tests replacing vhost kthread's with workqueues degrades the 
performance. Moreover, having thread management inside the vhost provides 
opportunity for optimization, at least for some workloads...
That said, I believe that switching vhost to use workqueues is not that 
good idea after all.
 
> Netperf:
> Two guests running netperf in parallel.
>                                  Without patches                  With 
patches
> 
> TCP_STREAM (10^6 bits/second)         975.45              978.88 
> TCP_RR (Trans/second)            20121              18820.82
> UDP_STREAM (10^6 bits/second)         1287.82                1184.5
> UDP_RR (Trans/second)            20766.72              19667.08
> Time a 4G iso download            2m 33 seconds           3m 02 seconds

--
Sincerely yours,
Mike.

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[RFC PATCH 0/4] cgroup aware workqueues Bandan Das <bsd@redhat.com> - 2016-03-18 23:20 +0100
  Re: [RFC PATCH 0/4] cgroup aware workqueues Tejun Heo <tj@kernel.org> - 2016-03-20 19:20 +0100
    Re: [RFC PATCH 0/4] cgroup aware workqueues Bandan Das <bsd@redhat.com> - 2016-03-21 18:40 +0100
  Re: [RFC PATCH 0/4] cgroup aware workqueues "Michael Rapoport" <RAPOPORT@il.ibm.com> - 2016-03-21 09:00 +0100
  Re: [RFC PATCH 0/4] cgroup aware workqueues Christian Borntraeger <borntraeger@de.ibm.com> - 2016-03-21 09:30 +0100
    Re: [RFC PATCH 0/4] cgroup aware workqueues Bandan Das <bsd@redhat.com> - 2016-03-21 19:00 +0100
  Re: [RFC PATCH 0/4] cgroup aware workqueues Bandan Das <bsd@redhat.com> - 2016-03-21 18:50 +0100
    vhost threading model (was: Re: [RFC PATCH 0/4] cgroup aware workqueues) "Michael Rapoport" <RAPOPORT@il.ibm.com> - 2016-03-22 08:20 +0100
    Re: vhost threading model Bandan Das <bsd@redhat.com> - 2016-03-22 20:10 +0100
      Re: vhost threading model "Michael Rapoport" <RAPOPORT@il.ibm.com> - 2016-03-23 12:20 +0100
  Re: [RFC PATCH 0/4] cgroup aware workqueues Tejun Heo <tj@kernel.org> - 2016-03-30 19:10 +0200
    Re: [RFC PATCH 0/4] cgroup aware workqueues "Michael Rapoport" <RAPOPORT@il.ibm.com> - 2016-03-31 08:20 +0200
      Re: [RFC PATCH 0/4] cgroup aware workqueues Tejun Heo <tj@kernel.org> - 2016-03-31 19:20 +0200
        Re: [RFC PATCH 0/4] cgroup aware workqueues Bandan Das <bsd@redhat.com> - 2016-03-31 20:50 +0200

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