| Message ID | 20200320103041.129527-1-stefanha@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | virtio-pci: enable blk and scsi multi-queue by default | expand |
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 on SMP > guests because the completion interrupt is handled on the vCPU that submitted > the I/O request. This avoids IPIs inside the guest. > > 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 benchmark > results can vary noticably between runs.) > 3. Users may bind the application to the vCPU that handles completion > interrupts. > > 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 queue > for live migration compatibility. > > Random read performance: > IOPS > q=1 78k > q=32 104k +33% > > Boot time: > Duration > q=1 51s > q=32 1m41s +98% > > Guest configuration: 32 vCPUs, 101 virtio-blk-pci disks > > Previously measured results on a 4 vCPU guest were also positive but showed a > smaller 1-4% performance improvement. They are no longer valid because > significant event loop optimizations have been merged. > > 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 > > 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(-) > > -- > 2.24.1 >
For best case its really a good idea to configure default number of
queues to the number of CPU's.
For the series:
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
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] So this needs to be rebased wrt compat properties. I also see some comments from Cornelia, worth addressing. > Enabling multi-queue on virtio-pci storage devices improves performance on SMP > guests because the completion interrupt is handled on the vCPU that submitted > the I/O request. This avoids IPIs inside the guest. > > 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 benchmark > results can vary noticably between runs.) > 3. Users may bind the application to the vCPU that handles completion > interrupts. > > 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 queue > for live migration compatibility. > > Random read performance: > IOPS > q=1 78k > q=32 104k +33% > > Boot time: > Duration > q=1 51s > q=32 1m41s +98% > > Guest configuration: 32 vCPUs, 101 virtio-blk-pci disks > > Previously measured results on a 4 vCPU guest were also positive but showed a > smaller 1-4% performance improvement. They are no longer valid because > significant event loop optimizations have been merged. > > 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 > > 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(-) > > -- > 2.24.1 >
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] Enabling multi-queue on virtio-pci storage devices improves performance on SMP guests because the completion interrupt is handled on the vCPU that submitted the I/O request. This avoids IPIs inside the guest. 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 benchmark results can vary noticably between runs.) 3. Users may bind the application to the vCPU that handles completion interrupts. 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 queue for live migration compatibility. Random read performance: IOPS q=1 78k q=32 104k +33% Boot time: Duration q=1 51s q=32 1m41s +98% Guest configuration: 32 vCPUs, 101 virtio-blk-pci disks Previously measured results on a 4 vCPU guest were also positive but showed a smaller 1-4% performance improvement. They are no longer valid because significant event loop optimizations have been merged. 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 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(-)