Re: [PATCH 2/4] block: Implement a blk_yield function to voluntarily give up the I/O scheduler.

[Jeff Moyer]

Jens Axboe <jens.axboe@xxxxxxxxxx> writes:

> On Wed, Apr 14 2010, Vivek Goyal wrote:

>> > @@ -1887,6 +1891,9 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
>> >  
>> >  	cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
>> >  	cfqq->nr_sectors += blk_rq_sectors(rq);
>> > +
>> > +	if (cfq_cfqq_yield(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
>> > +		cfq_yield_cfqq(cfqd, cfqq);
>> 
>> Jeff,
>> 
>> I am wondering if cfq_select_queue() will be a better place for yielding
>> the queue.
>> 
>> 	if (cfq_cfqq_yield(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
>> 			goto expire;
>> 
>> We can avoid one unnecessary __blk_run_queue().
>
> Agree, doing it on insert is not the right place.

I see where you're coming from, but that makes things quite a bit
trickier.  I look forward to the review of *that* patch.  ;-)

Cheers,
Jeff
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