Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH] block: virtio_blk: don't hold spin lock during world switch | Date | Fri, 30 May 2014 15:35:41 +0930 |
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Ming Lei <ming.lei@canonical.com> writes: > 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 > > fio script: > [global] > direct=1 > bsrange=4k-4k > timeout=10 > numjobs=4 > ioengine=libaio > iodepth=64 > > filename=/dev/vdc > group_reporting=1 > > [f1] > rw=randread > > Cc: Rusty Russell <rusty@rustcorp.com.au> > Cc: "Michael S. Tsirkin" <mst@redhat.com> > Cc: virtualization@lists.linux-foundation.org > Signed-off-by: Ming Lei <ming.lei@canonical.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Thanks! Rusty.
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