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

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
hw/block/virtio-blk.c
View File

@ -1147,6 +1147,9 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
error_setg(errp, "Device needs media, but drive is empty");
return;
}
if (conf->num_queues == VIRTIO_BLK_AUTO_NUM_QUEUES) {
conf->num_queues = 1;
}
if (!conf->num_queues) {
error_setg(errp, "num-queues property must be larger than 0");
return;
@ -1281,7 +1284,8 @@ static Property virtio_blk_properties[] = {
#endif
DEFINE_PROP_BIT("request-merging", VirtIOBlock, conf.request_merging, 0,
true),
DEFINE_PROP_UINT16("num-queues", VirtIOBlock, conf.num_queues, 1),
DEFINE_PROP_UINT16("num-queues", VirtIOBlock, conf.num_queues,
VIRTIO_BLK_AUTO_NUM_QUEUES),
DEFINE_PROP_UINT16("queue-size", VirtIOBlock, conf.queue_size, 256),
DEFINE_PROP_BOOL("seg-max-adjust", VirtIOBlock, conf.seg_max_adjust, true),
DEFINE_PROP_LINK("iothread", VirtIOBlock, conf.iothread, TYPE_IOTHREAD,

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);

7
hw/virtio/virtio-blk-pci.c
View File

@ -50,9 +50,14 @@ static void virtio_blk_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
{
VirtIOBlkPCI *dev = VIRTIO_BLK_PCI(vpci_dev);
DeviceState *vdev = DEVICE(&dev->vdev);
VirtIOBlkConf *conf = &dev->vdev.conf;
if (conf->num_queues == VIRTIO_BLK_AUTO_NUM_QUEUES) {
conf->num_queues = virtio_pci_optimal_num_queues(0);
}
if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
vpci_dev->nvectors = dev->vdev.conf.num_queues + 1;
vpci_dev->nvectors = conf->num_queues + 1;
}
qdev_realize(vdev, BUS(&vpci_dev->bus), errp);

2
include/hw/virtio/virtio-blk.h
View File

@ -30,6 +30,8 @@ struct virtio_blk_inhdr
unsigned char status;
};
#define VIRTIO_BLK_AUTO_NUM_QUEUES UINT16_MAX
struct VirtIOBlkConf
{
BlockConf conf;