Re: tools/virtiofs: Multi threading seems to hurt performance

[Vivek Goyal]

On Mon, Sep 21, 2020 at 09:50:19AM +0100, Dr. David Alan Gilbert wrote:
> * 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).
> > 
> > I am especially more interested in getting performance better for
> > single process in client. If that suffers, then it is pretty bad.
> > 
> > Especially look at randread, randwrite, seqwrite performance. seqread
> > seems pretty good anyway.
> > 
> > If I don't run who test suite and just ran randread-psync job,
> > my throughput jumps from around 40MB/s to 60MB/s. That's a huge
> > jump I would say.
> > 
> > Thoughts?
> 
> What's your host setup; how many cores has the host got and how many did
> you give the guest?

Got 2 processors on host with 16 cores in each processor. With
hyperthreading enabled, it makes 32 logical cores on each processor and
that makes 64 logical cores on host.

I have given 32 to guest.

Vivek