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Mon, 21 Sep 2020 09:35:16 -0400 (EDT) Date: Mon, 21 Sep 2020 09:35:16 -0400 From: Vivek Goyal To: "Dr. David Alan Gilbert" Subject: Re: tools/virtiofs: Multi threading seems to hurt performance Message-ID: <20200921133516.GA13362@redhat.com> References: <20200918213436.GA3520@redhat.com> <20200921085019.GB3221@work-vm> MIME-Version: 1.0 In-Reply-To: <20200921085019.GB3221@work-vm> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=vgoyal@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=vgoyal@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/21 01:44:53 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.455, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: virtio-fs-list , qemu-devel@nongnu.org, Stefan Hajnoczi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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