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Re: [Xen-devel] [PATCH v2] xen/blkfront: convert to blk-mq APIs

On 07/11/2015 07:30 AM, Bob Liu wrote:
Note: This patch is based on original work of Arianna's internship for
GNOME's Outreach Program for Women.

Great to see this finally get prepped to go in!

Only one hardware queue is used now, so there is no performance change.

I would hope that the blk-mq path, even with one queue, is a perf win over the old interface. So I'm not sure that is correct. But the bigger win will be with more queues, of course.

The legacy non-mq code is deleted completely which is the same as other
drivers like virtio, mtip, and nvme.

Also dropped one unnecessary holding of info->io_lock when calling

Changes in v2:
  - Reorganized blk_mq_queue_rq()
  - Restored most io_locks in place

Looks good to me. The most common error case is the busy-out not stopping queues, or not restarting them at completion. But that all looks fine.

I would, however, rename blk_mq_queue_rq(). It sounds like a core function. blkif_queue_rq() would be more appropriate.

Signed-off-by: Arianna Avanzini <avanzini.arianna@xxxxxxxxx>
Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>

Acked-by: Jens Axboe <axboe@xxxxxx>

Jens Axboe

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