Dongli Zhang
2019-Mar-27 10:36 UTC
[PATCH 0/2] Limit number of hw queues by nr_cpu_ids for virtio-blk and virtio-scsi
When tag_set->nr_maps is 1, the block layer limits the number of hw queues by nr_cpu_ids. No matter how many hw queues are use by virtio-blk/virtio-scsi, as they both have (tag_set->nr_maps == 1), they can use at most nr_cpu_ids hw queues. In addition, specifically for pci scenario, when the 'num-queues' specified by qemu is more than maxcpus, virtio-blk/virtio-scsi would not be able to allocate more than maxcpus vectors in order to have a vector for each queue. As a result, they fall back into MSI-X with one vector for config and one shared for queues. Considering above reasons, this patch set limits the number of hw queues used by nr_cpu_ids for both virtio-blk and virtio-scsi. ------------------------------------------------------------- Here is test result of virtio-scsi: qemu cmdline: -smp 2,maxcpus=4, \ -device virtio-scsi-pci,id=scsi0,num_queues=8, \ -device scsi-hd,drive=drive0,bus=scsi0.0,channel=0,scsi-id=0,lun=0, \ -drive file=test.img,if=none,id=drive0 Although maxcpus=4 and num_queues=8, 4 queues are used while 2 interrupts are allocated. # cat /proc/interrupts ... ... 24: 0 0 PCI-MSI 65536-edge virtio0-config 25: 0 369 PCI-MSI 65537-edge virtio0-virtqueues ... ... # /sys/block/sda/mq/ 0 1 2 3 ------> 4 queues although qemu sets num_queues=8 With the patch set, there is per-queue interrupt. # cat /proc/interrupts 24: 0 0 PCI-MSI 65536-edge virtio0-config 25: 0 0 PCI-MSI 65537-edge virtio0-control 26: 0 0 PCI-MSI 65538-edge virtio0-event 27: 296 0 PCI-MSI 65539-edge virtio0-request 28: 0 139 PCI-MSI 65540-edge virtio0-request 29: 0 0 PCI-MSI 65541-edge virtio0-request 30: 0 0 PCI-MSI 65542-edge virtio0-request # ls /sys/block/sda/mq 0 1 2 3 ------------------------------------------------------------- Here is test result of virtio-blk: qemu cmdline: -smp 2,maxcpus=4, -device virtio-blk-pci,drive=drive-virtio-disk0,id=virtio-disk0,num-queues=8 -drive test.img,format=raw,if=none,id=drive-virtio-disk0 Although maxcpus=4 and num-queues=8, 4 queues are used while 2 interrupts are allocated. # cat /proc/interrupts ... ... 24: 0 0 PCI-MSI 65536-edge virtio0-config 25: 0 65 PCI-MSI 65537-edge virtio0-virtqueues ... ... # ls /sys/block/vda/mq 0 1 2 3 -------> 4 queues although qemu sets num_queues=8 With the patch set, there is per-queue interrupt. # cat /proc/interrupts 24: 0 0 PCI-MSI 65536-edge virtio0-config 25: 64 0 PCI-MSI 65537-edge virtio0-req.0 26: 0 10290 PCI-MSI 65538-edge virtio0-req.1 27: 0 0 PCI-MSI 65539-edge virtio0-req.2 28: 0 0 PCI-MSI 65540-edge virtio0-req.3 # ls /sys/block/vda/mq/ 0 1 2 3 Reference: https://lore.kernel.org/lkml/e4afe4c5-0262-4500-aeec-60f30734b4fc at default/ Thank you very much! Dongli Zhang
Dongli Zhang
2019-Mar-27 10:36 UTC
[PATCH 1/2] virtio-blk: limit number of hw queues by nr_cpu_ids
When tag_set->nr_maps is 1, the block layer limits the number of hw queues by nr_cpu_ids. No matter how many hw queues are used by virtio-blk, as it has (tag_set->nr_maps == 1), it can use at most nr_cpu_ids hw queues. In addition, specifically for pci scenario, when the 'num-queues' specified by qemu is more than maxcpus, virtio-blk would not be able to allocate more than maxcpus vectors in order to have a vector for each queue. As a result, it falls back into MSI-X with one vector for config and one shared for queues. Considering above reasons, this patch limits the number of hw queues used by virtio-blk by nr_cpu_ids. Signed-off-by: Dongli Zhang <dongli.zhang at oracle.com> --- drivers/block/virtio_blk.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 4bc083b..b83cb45 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -513,6 +513,8 @@ static int init_vq(struct virtio_blk *vblk) if (err) num_vqs = 1; + num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs); + vblk->vqs = kmalloc_array(num_vqs, sizeof(*vblk->vqs), GFP_KERNEL); if (!vblk->vqs) return -ENOMEM; -- 2.7.4
Dongli Zhang
2019-Mar-27 10:36 UTC
[PATCH 2/2] scsi: virtio_scsi: limit number of hw queues by nr_cpu_ids
When tag_set->nr_maps is 1, the block layer limits the number of hw queues by nr_cpu_ids. No matter how many hw queues are used by virtio-scsi, as it has (tag_set->nr_maps == 1), it can use at most nr_cpu_ids hw queues. In addition, specifically for pci scenario, when the 'num_queues' specified by qemu is more than maxcpus, virtio-scsi would not be able to allocate more than maxcpus vectors in order to have a vector for each queue. As a result, it falls back into MSI-X with one vector for config and one shared for queues. Considering above reasons, this patch limits the number of hw queues used by virtio-scsi by nr_cpu_ids. Signed-off-by: Dongli Zhang <dongli.zhang at oracle.com> --- drivers/scsi/virtio_scsi.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c index 8af0177..9c4a3e1 100644 --- a/drivers/scsi/virtio_scsi.c +++ b/drivers/scsi/virtio_scsi.c @@ -793,6 +793,7 @@ static int virtscsi_probe(struct virtio_device *vdev) /* We need to know how many queues before we allocate. */ num_queues = virtscsi_config_get(vdev, num_queues) ? : 1; + num_queues = min_t(unsigned int, nr_cpu_ids, num_queues); num_targets = virtscsi_config_get(vdev, max_target) + 1; -- 2.7.4
Dongli Zhang
2019-Apr-08 13:57 UTC
[PATCH 0/2] Limit number of hw queues by nr_cpu_ids for virtio-blk and virtio-scsi
ping? Thank you very much! Dongli Zhang On 03/27/2019 06:36 PM, Dongli Zhang wrote:> When tag_set->nr_maps is 1, the block layer limits the number of hw queues > by nr_cpu_ids. No matter how many hw queues are use by > virtio-blk/virtio-scsi, as they both have (tag_set->nr_maps == 1), they > can use at most nr_cpu_ids hw queues. > > In addition, specifically for pci scenario, when the 'num-queues' specified > by qemu is more than maxcpus, virtio-blk/virtio-scsi would not be able to > allocate more than maxcpus vectors in order to have a vector for each > queue. As a result, they fall back into MSI-X with one vector for config > and one shared for queues. > > Considering above reasons, this patch set limits the number of hw queues > used by nr_cpu_ids for both virtio-blk and virtio-scsi. > > ------------------------------------------------------------- > > Here is test result of virtio-scsi: > > qemu cmdline: > > -smp 2,maxcpus=4, \ > -device virtio-scsi-pci,id=scsi0,num_queues=8, \ > -device scsi-hd,drive=drive0,bus=scsi0.0,channel=0,scsi-id=0,lun=0, \ > -drive file=test.img,if=none,id=drive0 > > Although maxcpus=4 and num_queues=8, 4 queues are used while 2 interrupts > are allocated. > > # cat /proc/interrupts > ... ... > 24: 0 0 PCI-MSI 65536-edge virtio0-config > 25: 0 369 PCI-MSI 65537-edge virtio0-virtqueues > ... ... > > # /sys/block/sda/mq/ > 0 1 2 3 ------> 4 queues although qemu sets num_queues=8 > > > With the patch set, there is per-queue interrupt. > > # cat /proc/interrupts > 24: 0 0 PCI-MSI 65536-edge virtio0-config > 25: 0 0 PCI-MSI 65537-edge virtio0-control > 26: 0 0 PCI-MSI 65538-edge virtio0-event > 27: 296 0 PCI-MSI 65539-edge virtio0-request > 28: 0 139 PCI-MSI 65540-edge virtio0-request > 29: 0 0 PCI-MSI 65541-edge virtio0-request > 30: 0 0 PCI-MSI 65542-edge virtio0-request > > # ls /sys/block/sda/mq > 0 1 2 3 > > ------------------------------------------------------------- > > Here is test result of virtio-blk: > > qemu cmdline: > > -smp 2,maxcpus=4, > -device virtio-blk-pci,drive=drive-virtio-disk0,id=virtio-disk0,num-queues=8 > -drive test.img,format=raw,if=none,id=drive-virtio-disk0 > > Although maxcpus=4 and num-queues=8, 4 queues are used while 2 interrupts > are allocated. > > # cat /proc/interrupts > ... ... > 24: 0 0 PCI-MSI 65536-edge virtio0-config > 25: 0 65 PCI-MSI 65537-edge virtio0-virtqueues > ... ... > > # ls /sys/block/vda/mq > 0 1 2 3 -------> 4 queues although qemu sets num_queues=8 > > > With the patch set, there is per-queue interrupt. > > # cat /proc/interrupts > 24: 0 0 PCI-MSI 65536-edge virtio0-config > 25: 64 0 PCI-MSI 65537-edge virtio0-req.0 > 26: 0 10290 PCI-MSI 65538-edge virtio0-req.1 > 27: 0 0 PCI-MSI 65539-edge virtio0-req.2 > 28: 0 0 PCI-MSI 65540-edge virtio0-req.3 > > # ls /sys/block/vda/mq/ > 0 1 2 3 > > > Reference: https://lore.kernel.org/lkml/e4afe4c5-0262-4500-aeec-60f30734b4fc at default/ > > Thank you very much! > > Dongli Zhang >
Stefan Hajnoczi
2019-Apr-10 13:12 UTC
[PATCH 1/2] virtio-blk: limit number of hw queues by nr_cpu_ids
On Wed, Mar 27, 2019 at 06:36:34PM +0800, Dongli Zhang wrote:> When tag_set->nr_maps is 1, the block layer limits the number of hw queues > by nr_cpu_ids. No matter how many hw queues are used by virtio-blk, as it > has (tag_set->nr_maps == 1), it can use at most nr_cpu_ids hw queues. > > In addition, specifically for pci scenario, when the 'num-queues' specified > by qemu is more than maxcpus, virtio-blk would not be able to allocate more > than maxcpus vectors in order to have a vector for each queue. As a result, > it falls back into MSI-X with one vector for config and one shared for > queues. > > Considering above reasons, this patch limits the number of hw queues used > by virtio-blk by nr_cpu_ids. > > Signed-off-by: Dongli Zhang <dongli.zhang at oracle.com> > --- > drivers/block/virtio_blk.c | 2 ++ > 1 file changed, 2 insertions(+)Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com> -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 455 bytes Desc: not available URL: <http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20190410/49ec4c11/attachment.sig>
Stefan Hajnoczi
2019-Apr-10 13:12 UTC
[PATCH 2/2] scsi: virtio_scsi: limit number of hw queues by nr_cpu_ids
On Wed, Mar 27, 2019 at 06:36:35PM +0800, Dongli Zhang wrote:> When tag_set->nr_maps is 1, the block layer limits the number of hw queues > by nr_cpu_ids. No matter how many hw queues are used by virtio-scsi, as it > has (tag_set->nr_maps == 1), it can use at most nr_cpu_ids hw queues. > > In addition, specifically for pci scenario, when the 'num_queues' specified > by qemu is more than maxcpus, virtio-scsi would not be able to allocate > more than maxcpus vectors in order to have a vector for each queue. As a > result, it falls back into MSI-X with one vector for config and one shared > for queues. > > Considering above reasons, this patch limits the number of hw queues used > by virtio-scsi by nr_cpu_ids. > > Signed-off-by: Dongli Zhang <dongli.zhang at oracle.com> > --- > drivers/scsi/virtio_scsi.c | 1 + > 1 file changed, 1 insertion(+)Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com> -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 455 bytes Desc: not available URL: <http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20190410/876ba129/attachment.sig>
Jens Axboe
2019-Apr-10 14:18 UTC
[PATCH 0/2] Limit number of hw queues by nr_cpu_ids for virtio-blk and virtio-scsi
On 3/27/19 4:36 AM, Dongli Zhang wrote:> When tag_set->nr_maps is 1, the block layer limits the number of hw queues > by nr_cpu_ids. No matter how many hw queues are use by > virtio-blk/virtio-scsi, as they both have (tag_set->nr_maps == 1), they > can use at most nr_cpu_ids hw queues. > > In addition, specifically for pci scenario, when the 'num-queues' specified > by qemu is more than maxcpus, virtio-blk/virtio-scsi would not be able to > allocate more than maxcpus vectors in order to have a vector for each > queue. As a result, they fall back into MSI-X with one vector for config > and one shared for queues. > > Considering above reasons, this patch set limits the number of hw queues > used by nr_cpu_ids for both virtio-blk and virtio-scsi.I picked both up for 5.1. -- Jens Axboe
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