Messages in this thread | | | Date | Thu, 29 May 2014 21:19:14 -0600 | From | Jens Axboe <> | Subject | Re: [PATCH] block: virtio_blk: don't hold spin lock during world switch |
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On 2014-05-29 20:49, Ming Lei wrote: > Firstly, it isn't necessary to hold lock of vblk->vq_lock > when notifying hypervisor about queued I/O. > > Secondly, virtqueue_notify() will cause world switch and > it may take long time on some hypervisors(such as, qemu-arm), > so it isn't good to hold the lock and block other vCPUs. > > On arm64 quad core VM(qemu-kvm), the patch can increase I/O > performance a lot with VIRTIO_RING_F_EVENT_IDX enabled: > - without the patch: 14K IOPS > - with the patch: 34K IOPS
Patch looks good to me. I don't see a hit on my qemu-kvm testing, but it definitely makes sense and I can see it hurting in other places.
-- Jens Axboe
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