Re: [Virtio-fs] tools/virtiofs: Multi threading seems to hurt performance

[Dr. David Alan Gilbert]

* Chirantan Ekbote (chirantan@chromium.org) wrote:
> On Sat, Sep 19, 2020 at 6:36 AM Vivek Goyal <vgoyal@redhat.com> wrote:
> >
> > Hi All,
> >
> > virtiofsd default thread pool size is 64. To me it feels that in most of
> > the cases thread pool size 1 performs better than thread pool size 64.
> >
> > I ran virtiofs-tests.
> >
> > https://github.com/rhvgoyal/virtiofs-tests
> >
> > And here are the comparision results. To me it seems that by default
> > we should switch to 1 thread (Till we can figure out how to make
> > multi thread performance better even when single process is doing
> > I/O in client).
> >
> 
> FWIW, we've observed the same behavior in crosvm. Using a thread pool
> for the virtiofs server consistently gave us worse performance than
> using a single thread.

Interesting; so it's not just us doing something silly!
It does feel like you *should* be able to get some benefit from multiple
threads; so I guess some more investigation needed at some time.

Dave

> Chirantan
> 
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-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK