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Date: Wed, 27 Mar 2019 18:36:34 +0800 From: Dongli Zhang <dongli.zhang@...cle.com> To: linux-scsi@...r.kernel.org, virtualization@...ts.linux-foundation.org, linux-block@...r.kernel.org Cc: mst@...hat.com, jasowang@...hat.com, axboe@...nel.dk, jejb@...ux.ibm.com, martin.petersen@...cle.com, cohuck@...hat.com, linux-kernel@...r.kernel.org Subject: [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@...cle.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
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