| Message ID | 20170810165255.20865-1-rjones@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Aug 10, 2017 at 05:52:55PM +0100, Richard W.M. Jones wrote: > Since Linux switched to blk-mq as the default in Linux commit > 5c279bd9e406 ("scsi: default to scsi-mq"), virtio-scsi LUNs consume > about 10x as much guest kernel memory. > > This commit allows you to choose the virtqueue size for each > virtio-scsi-pci controller like this: > > -device virtio-scsi-pci,id=scsi,virtqueue_size=16 > > The default is still 128 as before. Using smaller virtqueue_size > allows many more disks to be added to small memory virtual machines. > For a 1 vCPU, 500 MB, no swap VM I observed: > > With scsi-mq enabled (upstream kernel): 175 disks > -"- ditto -"- virtqueue_size=64: 318 disks > -"- ditto -"- virtqueue_size=16: 775 disks > With scsi-mq disabled (kernel before 5c279bd9e406): 1755 disks > > Note that to have any effect, this requires a kernel patch: > > https://lkml.org/lkml/2017/8/10/689 > > Signed-off-by: Richard W.M. Jones <rjones@redhat.com> Looks reasonable but pls remember to repost after the release. > --- > hw/scsi/virtio-scsi.c | 8 +++++--- > include/hw/virtio/virtio-scsi.h | 2 +- > 2 files changed, 6 insertions(+), 4 deletions(-) > > diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c > index eb639442d1..aca1909a59 100644 > --- a/hw/scsi/virtio-scsi.c > +++ b/hw/scsi/virtio-scsi.c > @@ -867,10 +867,10 @@ void virtio_scsi_common_realize(DeviceState *dev, > s->sense_size = VIRTIO_SCSI_SENSE_DEFAULT_SIZE; > s->cdb_size = VIRTIO_SCSI_CDB_DEFAULT_SIZE; > > - s->ctrl_vq = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, ctrl); > - s->event_vq = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, evt); > + s->ctrl_vq = virtio_add_queue(vdev, s->conf.virtqueue_size, ctrl); > + s->event_vq = virtio_add_queue(vdev, s->conf.virtqueue_size, evt); > for (i = 0; i < s->conf.num_queues; i++) { > - s->cmd_vqs[i] = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, cmd); > + s->cmd_vqs[i] = virtio_add_queue(vdev, s->conf.virtqueue_size, cmd); > } > } > > @@ -917,6 +917,8 @@ static void virtio_scsi_device_unrealize(DeviceState *dev, Error **errp) > > static Property virtio_scsi_properties[] = { > DEFINE_PROP_UINT32("num_queues", VirtIOSCSI, parent_obj.conf.num_queues, 1), > + DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSI, > + parent_obj.conf.virtqueue_size, 128), > DEFINE_PROP_UINT32("max_sectors", VirtIOSCSI, parent_obj.conf.max_sectors, > 0xFFFF), > DEFINE_PROP_UINT32("cmd_per_lun", VirtIOSCSI, parent_obj.conf.cmd_per_lun, > diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h > index de6ae5a9f6..4c0bcdb788 100644 > --- a/include/hw/virtio/virtio-scsi.h > +++ b/include/hw/virtio/virtio-scsi.h > @@ -32,7 +32,6 @@ > #define VIRTIO_SCSI(obj) \ > OBJECT_CHECK(VirtIOSCSI, (obj), TYPE_VIRTIO_SCSI) > > -#define VIRTIO_SCSI_VQ_SIZE 128 > #define VIRTIO_SCSI_MAX_CHANNEL 0 > #define VIRTIO_SCSI_MAX_TARGET 255 > #define VIRTIO_SCSI_MAX_LUN 16383 > @@ -48,6 +47,7 @@ typedef struct virtio_scsi_config VirtIOSCSIConfig; > > struct VirtIOSCSIConf { > uint32_t num_queues; > + uint32_t virtqueue_size; > uint32_t max_sectors; > uint32_t cmd_per_lun; > #ifdef CONFIG_VHOST_SCSI > -- > 2.13.1
On Thu, Aug 10, 2017 at 05:52:55PM +0100, Richard W.M. Jones wrote: > Since Linux switched to blk-mq as the default in Linux commit > 5c279bd9e406 ("scsi: default to scsi-mq"), virtio-scsi LUNs consume > about 10x as much guest kernel memory. > > This commit allows you to choose the virtqueue size for each > virtio-scsi-pci controller like this: > > -device virtio-scsi-pci,id=scsi,virtqueue_size=16 > > The default is still 128 as before. Using smaller virtqueue_size > allows many more disks to be added to small memory virtual machines. > For a 1 vCPU, 500 MB, no swap VM I observed: > > With scsi-mq enabled (upstream kernel): 175 disks > -"- ditto -"- virtqueue_size=64: 318 disks > -"- ditto -"- virtqueue_size=16: 775 disks > With scsi-mq disabled (kernel before 5c279bd9e406): 1755 disks > > Note that to have any effect, this requires a kernel patch: > > https://lkml.org/lkml/2017/8/10/689 > > Signed-off-by: Richard W.M. Jones <rjones@redhat.com> > --- > hw/scsi/virtio-scsi.c | 8 +++++--- > include/hw/virtio/virtio-scsi.h | 2 +- > 2 files changed, 6 insertions(+), 4 deletions(-) > > diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c > index eb639442d1..aca1909a59 100644 > --- a/hw/scsi/virtio-scsi.c > +++ b/hw/scsi/virtio-scsi.c > @@ -867,10 +867,10 @@ void virtio_scsi_common_realize(DeviceState *dev, > s->sense_size = VIRTIO_SCSI_SENSE_DEFAULT_SIZE; > s->cdb_size = VIRTIO_SCSI_CDB_DEFAULT_SIZE; > > - s->ctrl_vq = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, ctrl); > - s->event_vq = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, evt); > + s->ctrl_vq = virtio_add_queue(vdev, s->conf.virtqueue_size, ctrl); > + s->event_vq = virtio_add_queue(vdev, s->conf.virtqueue_size, evt); > for (i = 0; i < s->conf.num_queues; i++) { > - s->cmd_vqs[i] = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, cmd); > + s->cmd_vqs[i] = virtio_add_queue(vdev, s->conf.virtqueue_size, cmd); > } > } Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c index eb639442d1..aca1909a59 100644 --- a/hw/scsi/virtio-scsi.c +++ b/hw/scsi/virtio-scsi.c @@ -867,10 +867,10 @@ void virtio_scsi_common_realize(DeviceState *dev, s->sense_size = VIRTIO_SCSI_SENSE_DEFAULT_SIZE; s->cdb_size = VIRTIO_SCSI_CDB_DEFAULT_SIZE; - s->ctrl_vq = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, ctrl); - s->event_vq = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, evt); + s->ctrl_vq = virtio_add_queue(vdev, s->conf.virtqueue_size, ctrl); + s->event_vq = virtio_add_queue(vdev, s->conf.virtqueue_size, evt); for (i = 0; i < s->conf.num_queues; i++) { - s->cmd_vqs[i] = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, cmd); + s->cmd_vqs[i] = virtio_add_queue(vdev, s->conf.virtqueue_size, cmd); } } @@ -917,6 +917,8 @@ static void virtio_scsi_device_unrealize(DeviceState *dev, Error **errp) static Property virtio_scsi_properties[] = { DEFINE_PROP_UINT32("num_queues", VirtIOSCSI, parent_obj.conf.num_queues, 1), + DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSI, + parent_obj.conf.virtqueue_size, 128), DEFINE_PROP_UINT32("max_sectors", VirtIOSCSI, parent_obj.conf.max_sectors, 0xFFFF), DEFINE_PROP_UINT32("cmd_per_lun", VirtIOSCSI, parent_obj.conf.cmd_per_lun, diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h index de6ae5a9f6..4c0bcdb788 100644 --- a/include/hw/virtio/virtio-scsi.h +++ b/include/hw/virtio/virtio-scsi.h @@ -32,7 +32,6 @@ #define VIRTIO_SCSI(obj) \ OBJECT_CHECK(VirtIOSCSI, (obj), TYPE_VIRTIO_SCSI) -#define VIRTIO_SCSI_VQ_SIZE 128 #define VIRTIO_SCSI_MAX_CHANNEL 0 #define VIRTIO_SCSI_MAX_TARGET 255 #define VIRTIO_SCSI_MAX_LUN 16383 @@ -48,6 +47,7 @@ typedef struct virtio_scsi_config VirtIOSCSIConfig; struct VirtIOSCSIConf { uint32_t num_queues; + uint32_t virtqueue_size; uint32_t max_sectors; uint32_t cmd_per_lun; #ifdef CONFIG_VHOST_SCSI
Since Linux switched to blk-mq as the default in Linux commit 5c279bd9e406 ("scsi: default to scsi-mq"), virtio-scsi LUNs consume about 10x as much guest kernel memory. This commit allows you to choose the virtqueue size for each virtio-scsi-pci controller like this: -device virtio-scsi-pci,id=scsi,virtqueue_size=16 The default is still 128 as before. Using smaller virtqueue_size allows many more disks to be added to small memory virtual machines. For a 1 vCPU, 500 MB, no swap VM I observed: With scsi-mq enabled (upstream kernel): 175 disks -"- ditto -"- virtqueue_size=64: 318 disks -"- ditto -"- virtqueue_size=16: 775 disks With scsi-mq disabled (kernel before 5c279bd9e406): 1755 disks Note that to have any effect, this requires a kernel patch: https://lkml.org/lkml/2017/8/10/689 Signed-off-by: Richard W.M. Jones <rjones@redhat.com> --- hw/scsi/virtio-scsi.c | 8 +++++--- include/hw/virtio/virtio-scsi.h | 2 +- 2 files changed, 6 insertions(+), 4 deletions(-)