On 18/11/2014 15:06, Paolo Bonzini wrote:
>> > + /* don't submit until next completion for -EAGAIN of non plug case */
>> > + if (unlikely(!s->io_q.plugged)) {
>> > + return 0;
>> > + }
>> > +
> Is this an optimization or a fix for something?
Ah, if !io_q.plugged we must be in the -EAGAIN case, so no need to
"submit immediately if queue depth is above 2/3". Can you rewrite the
comment like this:
/* 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;
}
Paolo
