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Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: handling -EAGAIN for !s->io_q
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: handling -EAGAIN for !s->io_q.plugged case |
Date: |
Mon, 24 Nov 2014 12:38:56 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 |
On 24/11/2014 12:31, Ming Lei wrote:
> + /* don't submit until next completion for -EAGAIN of non plug case */
> + if (unlikely(!s->io_q.plugged)) {
> + return 0;
> + }
> +
> /* submit immediately if queue depth is above 2/3 */
> if (idx > s->io_q.size * 2 / 3) {
> return ioq_submit(s);
}
return 0;
so I fail to see why my proposal:
/* This is reached in two cases: queue not plugged but io_submit
* returned -EAGAIN, or queue plugged. In the latter case, start
* submitting some I/O if the queue is getting too full. In the
* former case, instead, wait until an I/O operation is completed.
*/
if (likely(idx <= s->io_q.size * 2 / 3) || unlikely(!s->io_q.plugged) {
return 0;
}
return ioq_submit(s);
was wrong. Can you explain?
Paolo