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Re: [PATCH v4 4/5] virtio-blk: default num_queues to -smp N
From: |
Pankaj Gupta |
Subject: |
Re: [PATCH v4 4/5] virtio-blk: default num_queues to -smp N |
Date: |
Thu, 28 May 2020 16:45:01 +0200 |
> 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.
>
> 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>
> ---
> include/hw/virtio/virtio-blk.h | 2 ++
> hw/block/virtio-blk.c | 6 +++++-
> hw/core/machine.c | 1 +
> hw/virtio/virtio-blk-pci.c | 7 ++++++-
> 4 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
> index 1e62f869b2..4e5e903f4a 100644
> --- a/include/hw/virtio/virtio-blk.h
> +++ b/include/hw/virtio/virtio-blk.h
> @@ -30,6 +30,8 @@ struct virtio_blk_inhdr
> unsigned char status;
> };
>
> +#define VIRTIO_BLK_AUTO_NUM_QUEUES UINT16_MAX
> +
> struct VirtIOBlkConf
> {
> BlockConf conf;
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index f5f6fc925e..3c36b38255 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -1135,6 +1135,9 @@ 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;
> @@ -1274,7 +1277,8 @@ 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,
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index df7664bc8d..4aba3bdd3c 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -29,6 +29,7 @@
> #include "migration/vmstate.h"
>
> GlobalProperty hw_compat_5_0[] = {
> + { "virtio-blk-device", "num-queues", "1"},
> { "virtio-scsi-device", "num_queues", "1"},
> { "vhost-scsi", "num_queues", "1"},
> { "vhost-user-scsi", "num_queues", "1"},
> diff --git a/hw/virtio/virtio-blk-pci.c b/hw/virtio/virtio-blk-pci.c
> index 28838fa958..2f0ede3863 100644
> --- a/hw/virtio/virtio-blk-pci.c
> +++ b/hw/virtio/virtio-blk-pci.c
> @@ -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_set_parent_bus(vdev, BUS(&vpci_dev->bus));
Looks good to me.
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
- [PATCH v4 1/5] virtio-pci: add virtio_pci_optimal_num_queues() helper, (continued)
- [PATCH v4 1/5] virtio-pci: add virtio_pci_optimal_num_queues() helper, Stefan Hajnoczi, 2020/05/27
- [PATCH v4 2/5] virtio-scsi: introduce a constant for fixed virtqueues, Stefan Hajnoczi, 2020/05/27
- [PATCH v4 3/5] virtio-scsi: default num_queues to -smp N, Stefan Hajnoczi, 2020/05/27
- [PATCH v4 4/5] virtio-blk: default num_queues to -smp N, Stefan Hajnoczi, 2020/05/27
- Re: [PATCH v4 4/5] virtio-blk: default num_queues to -smp N,
Pankaj Gupta <=
- [PATCH v4 5/5] vhost-user-blk: default num_queues to -smp N, Stefan Hajnoczi, 2020/05/27