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[79.183.139.129]) by smtp.gmail.com with ESMTPSA id i8sm18453706wrb.41.2020.03.29.06.49.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 29 Mar 2020 06:49:33 -0700 (PDT) Date: Sun, 29 Mar 2020 09:49:30 -0400 From: "Michael S. Tsirkin" To: Stefan Hajnoczi Subject: Re: [PATCH RESEND v3 0/4] virtio-pci: enable blk and scsi multi-queue by default Message-ID: <20200329094907-mutt-send-email-mst@kernel.org> References: <20200320103041.129527-1-stefanha@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200320103041.129527-1-stefanha@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 216.205.24.74 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: Fam Zheng , Kevin Wolf , Eduardo Habkost , slp@redhat.com, cohuck@redhat.com, qemu-devel@nongnu.org, Max Reitz , Paolo Bonzini , qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Mar 20, 2020 at 10:30:37AM +0000, Stefan Hajnoczi wrote: > v3: > * Add new performance results that demonstrate the scalability > * Mention that this is PCI-specific [Cornelia] > v2: > * Let the virtio-DEVICE-pci device select num-queues because the optimal > multi-queue configuration may differ between virtio-pci, virtio-mmio, = and > virtio-ccw [Cornelia] I'd like to queue it for merge after the release. If possible please ping me after the release to help make sure it didn't get dropped. Thanks! > Enabling multi-queue on virtio-pci storage devices improves performance o= n SMP > guests because the completion interrupt is handled on the vCPU that submi= tted > the I/O request. This avoids IPIs inside the guest. >=20 > Note that performance is unchanged in these cases: > 1. Uniprocessor guests. They don't have IPIs. > 2. Application threads might be scheduled on the sole vCPU that handles > completion interrupts purely by chance. (This is one reason why bench= mark > results can vary noticably between runs.) > 3. Users may bind the application to the vCPU that handles completion > interrupts. >=20 > Set the number of queues to the number of vCPUs by default on virtio-blk = and > virtio-scsi PCI devices. Older machine types continue to default to 1 qu= eue > for live migration compatibility. >=20 > Random read performance: > IOPS > q=3D1 78k > q=3D32 104k +33% >=20 > Boot time: > Duration > q=3D1 51s > q=3D32 1m41s +98% >=20 > Guest configuration: 32 vCPUs, 101 virtio-blk-pci disks >=20 > Previously measured results on a 4 vCPU guest were also positive but show= ed a > smaller 1-4% performance improvement. They are no longer valid because > significant event loop optimizations have been merged. >=20 > Stefan Hajnoczi (4): > virtio-scsi: introduce a constant for fixed virtqueues > virtio-scsi: default num_queues to -smp N > virtio-blk: default num_queues to -smp N > vhost-user-blk: default num_queues to -smp N >=20 > hw/block/vhost-user-blk.c | 6 +++++- > hw/block/virtio-blk.c | 6 +++++- > hw/core/machine.c | 5 +++++ > hw/scsi/vhost-scsi.c | 3 ++- > hw/scsi/vhost-user-scsi.c | 5 +++-- > hw/scsi/virtio-scsi.c | 13 +++++++++---- > hw/virtio/vhost-scsi-pci.c | 10 ++++++++-- > hw/virtio/vhost-user-blk-pci.c | 6 ++++++ > hw/virtio/vhost-user-scsi-pci.c | 10 ++++++++-- > hw/virtio/virtio-blk-pci.c | 9 ++++++++- > hw/virtio/virtio-scsi-pci.c | 10 ++++++++-- > include/hw/virtio/vhost-user-blk.h | 2 ++ > include/hw/virtio/virtio-blk.h | 2 ++ > include/hw/virtio/virtio-scsi.h | 5 +++++ > 14 files changed, 76 insertions(+), 16 deletions(-) >=20 > --=20 > 2.24.1 >=20