Re: [PATCH v6 5/7] virtio-scsi-pci: default num_queues to -smp N

[Raphael Norwitz]

On Tue, Aug 18, 2020 at 11:32 AM Stefan Hajnoczi <stefanha@redhat.com> wrote:
>
> Automatically size the number of virtio-scsi-pci, vhost-scsi-pci, and
> vhost-user-scsi-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.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>

> ---
>  include/hw/virtio/virtio-scsi.h |  2 ++
>  hw/core/machine.c               |  3 +++
>  hw/scsi/vhost-scsi.c            |  3 ++-
>  hw/scsi/vhost-user-scsi.c       |  3 ++-
>  hw/scsi/virtio-scsi.c           |  6 +++++-
>  hw/virtio/vhost-scsi-pci.c      | 10 +++++++---
>  hw/virtio/vhost-user-scsi-pci.c | 10 +++++++---
>  hw/virtio/virtio-scsi-pci.c     | 10 +++++++---
>  8 files changed, 35 insertions(+), 12 deletions(-)
>
> diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
> index 9f293bcb80..c0b8e4dd7e 100644
> --- a/include/hw/virtio/virtio-scsi.h
> +++ b/include/hw/virtio/virtio-scsi.h
> @@ -39,6 +39,8 @@
>  /* Number of virtqueues that are always present */
>  #define VIRTIO_SCSI_VQ_NUM_FIXED    2
>
> +#define VIRTIO_SCSI_AUTO_NUM_QUEUES UINT32_MAX
> +
>  typedef struct virtio_scsi_cmd_req VirtIOSCSICmdReq;
>  typedef struct virtio_scsi_cmd_resp VirtIOSCSICmdResp;
>  typedef struct virtio_scsi_ctrl_tmf_req VirtIOSCSICtrlTMFReq;
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index a6f7e4e8d7..9ee2aa0f7b 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -29,6 +29,9 @@
>  #include "migration/vmstate.h"
>
>  GlobalProperty hw_compat_5_1[] = {
> +    { "vhost-scsi", "num_queues", "1"},
> +    { "vhost-user-scsi", "num_queues", "1"},
> +    { "virtio-scsi-device", "num_queues", "1"},
>  };
>  const size_t hw_compat_5_1_len = G_N_ELEMENTS(hw_compat_5_1);
>
> diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
> index 13b05af29b..a83ffeefc8 100644
> --- a/hw/scsi/vhost-scsi.c
> +++ b/hw/scsi/vhost-scsi.c
> @@ -270,7 +270,8 @@ static Property vhost_scsi_properties[] = {
>      DEFINE_PROP_STRING("vhostfd", VirtIOSCSICommon, conf.vhostfd),
>      DEFINE_PROP_STRING("wwpn", VirtIOSCSICommon, conf.wwpn),
>      DEFINE_PROP_UINT32("boot_tpgt", VirtIOSCSICommon, conf.boot_tpgt, 0),
> -    DEFINE_PROP_UINT32("num_queues", VirtIOSCSICommon, conf.num_queues, 1),
> +    DEFINE_PROP_UINT32("num_queues", VirtIOSCSICommon, conf.num_queues,
> +                       VIRTIO_SCSI_AUTO_NUM_QUEUES),
>      DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSICommon, 
> conf.virtqueue_size,
>                         128),
>      DEFINE_PROP_BOOL("seg_max_adjust", VirtIOSCSICommon, conf.seg_max_adjust,
> diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
> index a8b821466f..7c0631656c 100644
> --- a/hw/scsi/vhost-user-scsi.c
> +++ b/hw/scsi/vhost-user-scsi.c
> @@ -162,7 +162,8 @@ static void vhost_user_scsi_unrealize(DeviceState *dev)
>  static Property vhost_user_scsi_properties[] = {
>      DEFINE_PROP_CHR("chardev", VirtIOSCSICommon, conf.chardev),
>      DEFINE_PROP_UINT32("boot_tpgt", VirtIOSCSICommon, conf.boot_tpgt, 0),
> -    DEFINE_PROP_UINT32("num_queues", VirtIOSCSICommon, conf.num_queues, 1),
> +    DEFINE_PROP_UINT32("num_queues", VirtIOSCSICommon, conf.num_queues,
> +                       VIRTIO_SCSI_AUTO_NUM_QUEUES),
>      DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSICommon, 
> conf.virtqueue_size,
>                         128),
>      DEFINE_PROP_UINT32("max_sectors", VirtIOSCSICommon, conf.max_sectors,
> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
> index eecdd05af5..3a71ea7097 100644
> --- a/hw/scsi/virtio-scsi.c
> +++ b/hw/scsi/virtio-scsi.c
> @@ -891,6 +891,9 @@ void virtio_scsi_common_realize(DeviceState *dev,
>      virtio_init(vdev, "virtio-scsi", VIRTIO_ID_SCSI,
>                  sizeof(VirtIOSCSIConfig));
>
> +    if (s->conf.num_queues == VIRTIO_SCSI_AUTO_NUM_QUEUES) {
> +        s->conf.num_queues = 1;
> +    }
>      if (s->conf.num_queues == 0 ||
>              s->conf.num_queues > VIRTIO_QUEUE_MAX - 
> VIRTIO_SCSI_VQ_NUM_FIXED) {
>          error_setg(errp, "Invalid number of queues (= %" PRIu32 "), "
> @@ -964,7 +967,8 @@ static void virtio_scsi_device_unrealize(DeviceState *dev)
>  }
>
>  static Property virtio_scsi_properties[] = {
> -    DEFINE_PROP_UINT32("num_queues", VirtIOSCSI, parent_obj.conf.num_queues, 
> 1),
> +    DEFINE_PROP_UINT32("num_queues", VirtIOSCSI, parent_obj.conf.num_queues,
> +                       VIRTIO_SCSI_AUTO_NUM_QUEUES),
>      DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSI,
>                                           parent_obj.conf.virtqueue_size, 
> 256),
>      DEFINE_PROP_BOOL("seg_max_adjust", VirtIOSCSI,
> diff --git a/hw/virtio/vhost-scsi-pci.c b/hw/virtio/vhost-scsi-pci.c
> index 06e814d30e..a6bb0dc60d 100644
> --- a/hw/virtio/vhost-scsi-pci.c
> +++ b/hw/virtio/vhost-scsi-pci.c
> @@ -47,11 +47,15 @@ static void vhost_scsi_pci_realize(VirtIOPCIProxy 
> *vpci_dev, Error **errp)
>  {
>      VHostSCSIPCI *dev = VHOST_SCSI_PCI(vpci_dev);
>      DeviceState *vdev = DEVICE(&dev->vdev);
> -    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
> +    VirtIOSCSIConf *conf = &dev->vdev.parent_obj.parent_obj.conf;
> +
> +    if (conf->num_queues == VIRTIO_SCSI_AUTO_NUM_QUEUES) {
> +        conf->num_queues =
> +            virtio_pci_optimal_num_queues(VIRTIO_SCSI_VQ_NUM_FIXED);
> +    }
>
>      if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
> -        vpci_dev->nvectors = vs->conf.num_queues +
> -                             VIRTIO_SCSI_VQ_NUM_FIXED + 1;
> +        vpci_dev->nvectors = conf->num_queues + VIRTIO_SCSI_VQ_NUM_FIXED + 1;
>      }
>
>      qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
> diff --git a/hw/virtio/vhost-user-scsi-pci.c b/hw/virtio/vhost-user-scsi-pci.c
> index ab6dfb71a9..25e97ca54e 100644
> --- a/hw/virtio/vhost-user-scsi-pci.c
> +++ b/hw/virtio/vhost-user-scsi-pci.c
> @@ -53,11 +53,15 @@ static void vhost_user_scsi_pci_realize(VirtIOPCIProxy 
> *vpci_dev, Error **errp)
>  {
>      VHostUserSCSIPCI *dev = VHOST_USER_SCSI_PCI(vpci_dev);
>      DeviceState *vdev = DEVICE(&dev->vdev);
> -    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
> +    VirtIOSCSIConf *conf = &dev->vdev.parent_obj.parent_obj.conf;
> +
> +    if (conf->num_queues == VIRTIO_SCSI_AUTO_NUM_QUEUES) {
> +        conf->num_queues =
> +            virtio_pci_optimal_num_queues(VIRTIO_SCSI_VQ_NUM_FIXED);
> +    }
>
>      if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
> -        vpci_dev->nvectors = vs->conf.num_queues +
> -                             VIRTIO_SCSI_VQ_NUM_FIXED + 1;
> +        vpci_dev->nvectors = conf->num_queues + VIRTIO_SCSI_VQ_NUM_FIXED + 1;
>      }
>
>      qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
> diff --git a/hw/virtio/virtio-scsi-pci.c b/hw/virtio/virtio-scsi-pci.c
> index 3ff9eb7ef6..fa4b3bfb50 100644
> --- a/hw/virtio/virtio-scsi-pci.c
> +++ b/hw/virtio/virtio-scsi-pci.c
> @@ -46,13 +46,17 @@ static void virtio_scsi_pci_realize(VirtIOPCIProxy 
> *vpci_dev, Error **errp)
>  {
>      VirtIOSCSIPCI *dev = VIRTIO_SCSI_PCI(vpci_dev);
>      DeviceState *vdev = DEVICE(&dev->vdev);
> -    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
>      DeviceState *proxy = DEVICE(vpci_dev);
> +    VirtIOSCSIConf *conf = &dev->vdev.parent_obj.conf;
>      char *bus_name;
>
> +    if (conf->num_queues == VIRTIO_SCSI_AUTO_NUM_QUEUES) {
> +        conf->num_queues =
> +            virtio_pci_optimal_num_queues(VIRTIO_SCSI_VQ_NUM_FIXED);
> +    }
> +
>      if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
> -        vpci_dev->nvectors = vs->conf.num_queues +
> -                             VIRTIO_SCSI_VQ_NUM_FIXED + 1;
> +        vpci_dev->nvectors = conf->num_queues + VIRTIO_SCSI_VQ_NUM_FIXED + 1;
>      }
>
>      /*
> --
> 2.26.2
>