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 They are no longer valid because 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 >
