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virtio-blk-pci: default num_queues to -smp N

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Automatically size the number of virtio-blk-pci request virtqueues to
match the number of vCPUs.  Other transports continue to default to 1
request virtqueue.

A 1:1 virtqueue:vCPU mapping ensures that completion interrupts are
handled on the same vCPU that submitted the request.  No IPI is
necessary to complete an I/O request and performance is improved.  The
maximum number of MSI-X vectors and virtqueues limit are respected.

Performance improves from 78k to 104k IOPS on a 32 vCPU guest with 101
virtio-blk-pci devices (ioengine=libaio, iodepth=1, bs=4k, rw=randread
with NVMe storage).

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Message-Id: <20200818143348.310613-7-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2020-08-18 15:33:47 +01:00 • committed by Michael S. Tsirkin
parent 6a55882284
commit 9445e1e15e
4 changed files with 14 additions and 2 deletions
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1
hw/core/machine.c
View file

@ -31,6 +31,7 @@
GlobalProperty hw_compat_5_1[] = {
{ "vhost-scsi", "num_queues", "1"},
{ "vhost-user-scsi", "num_queues", "1"},
{ "virtio-blk-device", "num-queues", "1"},
{ "virtio-scsi-device", "num_queues", "1"},
};
const size_t hw_compat_5_1_len = G_N_ELEMENTS(hw_compat_5_1);