linux-kernel - Re: [PATCH 1/5] cfq-iosched: Don't group

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Message-ID: <20160111154019.GH6262@quack.suse.cz>
Date:	Mon, 11 Jan 2016 16:40:19 +0100
From:	Jan Kara <jack@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	Jan Kara <jack@...e.cz>, axboe@...nel.dk,
	linux-kernel@...r.kernel.org, Jeff Moyer <jmoyer@...hat.com>,
	Jan Kara <jack@...e.com>
Subject: Re: [PATCH 1/5] cfq-iosched: Don't group_idle if cfqq has big
 thinktime

On Fri 08-01-16 11:58:31, Tejun Heo wrote:
> Hello, Jan.
> 
> On Thu, Jan 07, 2016 at 04:28:12PM +0100, Jan Kara wrote:
> > @@ -2947,8 +2948,13 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
> >  		return;
> >  	}
> >  
> > -	/* There are other queues in the group, don't do group idle */
> > -	if (group_idle && cfqq->cfqg->nr_cfqq > 1)
> > +	/*
> > +	 * There are other queues in the group or this is the only group and
> > +	 * it has too big thinktime, don't do group idle.
> > +	 */
> > +	if (group_idle &&
> > +	    (cfqq->cfqg->nr_cfqq > 1 ||
> > +	     !cfq_io_thinktime_big(cfqd, &st->ttime, true)))
> >  		return;
> 
> Is the negation in front of the cfq_io_thinktime_big() right?  That
> doesn't seem to match the comment or description.  What am I missing?

Ah, you are right! I wanted to make arming of group_idle timer consistent
with what we test in cfq_should_idle() for normal idle timer but I
accidentally reverted the condition. I'll fix this.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR