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Tue, 22 Sep 2020 13:42:55 -0400 (EDT) Date: Tue, 22 Sep 2020 13:42:55 -0400 From: Vivek Goyal To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Subject: Re: [PATCH] virtiofsd: Used glib "shared" thread pool Message-ID: <20200922174255.GC57620@redhat.com> References: <20200921213216.GE13362@redhat.com> <20200922125957.GN1989025@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200922125957.GN1989025@redhat.com> 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=iso-8859-1 Content-Transfer-Encoding: 8bit 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 = 2020/09/22 02:07:04 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 , Miklos Szeredi , qemu-devel@nongnu.org, Stefan Hajnoczi , "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Sep 22, 2020 at 01:59:57PM +0100, Daniel P. Berrangé wrote: > On Mon, Sep 21, 2020 at 05:32:16PM -0400, Vivek Goyal wrote: > > glib offers thread pools and it seems to support "exclusive" and "shared" > > thread pools. > > > > https://developer.gnome.org/glib/stable/glib-Thread-Pools.html#g-thread-pool-new > > > > Currently we use "exlusive" thread pools but its performance seems to be > > poor. I tried using "shared" thread pools and performance seems much > > better. I posted performance results here. > > > > https://www.redhat.com/archives/virtio-fs/2020-September/msg00080.html > > > > So lets switch to shared thread pools. We can think of making it optional > > once somebody can show in what cases exclusive thread pools offer better > > results. For now, my simple performance tests across the board see > > better results with shared thread pools. > > I'm really curious why there's any perf difference between shared and > exclusive thread pools in the GLib impl. > > Looking at the code the main difference between the two is appears to > be around the way threads are spawned, specifically around the scheduler > attributes assigned. > > In the shared case, the threads in the pool will have their scheduler > attributes copied from the very first thread that calls g_thread_pool_new. > > In the exclusive case, the threads in the pool will inherit their > scheduler attributes from the thread which pushs the job that > causes the worker thread to be created. > > By schedular attributes, I mean all the items in the 'struct schedattr' > filled by sched_getattr() > > IOW, if threads in virtiofsd have varying schedular attributes this > could possibly explain the difference in performance you see between > the two setups. Hi Daniel, Few things. - I think scheduler attributes are same for the thread creating pool as well as for thread pushing the job for virtiofsd. - My glib2 is old (2.58.3) and I think that did not have sched_getattr() stuff. - One difference I noticed is that in case of shared pool, it does not create extra threads if client is doing one request at a time. While exclusive pool seemed to push every request to a new thread in pool in sort of round robin fashion. It feels keeping requests being served from same thread helps in this particilar workload case. Thanks Vivek > > > > > Signed-off-by: Vivek Goyal > > --- > > tools/virtiofsd/fuse_virtio.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > Index: qemu/tools/virtiofsd/fuse_virtio.c > > =================================================================== > > --- qemu.orig/tools/virtiofsd/fuse_virtio.c 2020-09-21 17:28:27.444438015 -0400 > > +++ qemu/tools/virtiofsd/fuse_virtio.c 2020-09-21 17:28:30.584568910 -0400 > > @@ -695,7 +695,7 @@ static void *fv_queue_thread(void *opaqu > > struct fuse_session *se = qi->virtio_dev->se; > > GThreadPool *pool; > > > > - pool = g_thread_pool_new(fv_queue_worker, qi, se->thread_pool_size, TRUE, > > + pool = g_thread_pool_new(fv_queue_worker, qi, se->thread_pool_size, FALSE, > > NULL); > > if (!pool) { > > fuse_log(FUSE_LOG_ERR, "%s: g_thread_pool_new failed\n", __func__); > > > > > > Regards, > Daniel > -- > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 22 Sep 2020 13:42:55 -0400 From: Vivek Goyal Message-ID: <20200922174255.GC57620@redhat.com> References: <20200921213216.GE13362@redhat.com> <20200922125957.GN1989025@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20200922125957.GN1989025@redhat.com> Subject: Re: [Virtio-fs] [PATCH] virtiofsd: Used glib "shared" thread pool List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Cc: virtio-fs-list , Miklos Szeredi , qemu-devel@nongnu.org On Tue, Sep 22, 2020 at 01:59:57PM +0100, Daniel P. Berrang=E9 wrote: > On Mon, Sep 21, 2020 at 05:32:16PM -0400, Vivek Goyal wrote: > > glib offers thread pools and it seems to support "exclusive" and "share= d" > > thread pools. > >=20 > > https://developer.gnome.org/glib/stable/glib-Thread-Pools.html#g-thread= -pool-new > >=20 > > Currently we use "exlusive" thread pools but its performance seems to be > > poor. I tried using "shared" thread pools and performance seems much > > better. I posted performance results here. > >=20 > > https://www.redhat.com/archives/virtio-fs/2020-September/msg00080.html > >=20 > > So lets switch to shared thread pools. We can think of making it option= al > > once somebody can show in what cases exclusive thread pools offer better > > results. For now, my simple performance tests across the board see > > better results with shared thread pools. >=20 > I'm really curious why there's any perf difference between shared and > exclusive thread pools in the GLib impl. >=20 > Looking at the code the main difference between the two is appears to > be around the way threads are spawned, specifically around the scheduler > attributes assigned. >=20 > In the shared case, the threads in the pool will have their scheduler > attributes copied from the very first thread that calls g_thread_pool_new. >=20 > In the exclusive case, the threads in the pool will inherit their > scheduler attributes from the thread which pushs the job that > causes the worker thread to be created. >=20 > By schedular attributes, I mean all the items in the 'struct schedattr' > filled by sched_getattr() >=20 > IOW, if threads in virtiofsd have varying schedular attributes this > could possibly explain the difference in performance you see between > the two setups. Hi Daniel, Few things. - I think scheduler attributes are same for the thread creating pool as well as for thread pushing the job for virtiofsd. - My glib2 is old (2.58.3) and I think that did not have sched_getattr() stuff. - One difference I noticed is that in case of shared pool, it does not create extra threads if client is doing one request at a time. While exclusive pool seemed to push every request to a new thread in pool in sort of round robin fashion. It feels keeping requests being served from same thread helps in this particilar workload case. Thanks Vivek >=20 > >=20 > > Signed-off-by: Vivek Goyal > > --- > > tools/virtiofsd/fuse_virtio.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > >=20 > > Index: qemu/tools/virtiofsd/fuse_virtio.c > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > --- qemu.orig/tools/virtiofsd/fuse_virtio.c 2020-09-21 17:28:27.4444380= 15 -0400 > > +++ qemu/tools/virtiofsd/fuse_virtio.c 2020-09-21 17:28:30.584568910 -0= 400 > > @@ -695,7 +695,7 @@ static void *fv_queue_thread(void *opaqu > > struct fuse_session *se =3D qi->virtio_dev->se; > > GThreadPool *pool; > > =20 > > - pool =3D g_thread_pool_new(fv_queue_worker, qi, se->thread_pool_si= ze, TRUE, > > + pool =3D g_thread_pool_new(fv_queue_worker, qi, se->thread_pool_si= ze, FALSE, > > NULL); > > if (!pool) { > > fuse_log(FUSE_LOG_ERR, "%s: g_thread_pool_new failed\n", __fun= c__); > >=20 > >=20 >=20 > Regards, > Daniel > --=20 > |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| > |: https://libvirt.org -o- https://fstop138.berrange.c= om :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|