diff options
author | Ming Lei <ming.lei@canonical.com> | 2014-05-30 02:49:29 (GMT) |
---|---|---|
committer | Jens Axboe <axboe@fb.com> | 2014-05-30 14:19:39 (GMT) |
commit | e8edca6f7f92234202d6dd163c118ef495244d7c (patch) | |
tree | 3546ab7cd1062b0cad3007818c08e468aa189a0c /drivers/block/mtip32xx/mtip32xx.c | |
parent | f89ca166460e84620db73d4542f28d34c40a8917 (diff) | |
download | linux-e8edca6f7f92234202d6dd163c118ef495244d7c.tar.xz |
block: virtio_blk: don't hold spin lock during world switch
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>
Cc: stable@kernel.org # 3.13+
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'drivers/block/mtip32xx/mtip32xx.c')
0 files changed, 0 insertions, 0 deletions