linux-ext4 - Re: [PATCH 1/3] block: Implement a blk_yield function to voluntarily give up the I/O scheduler.

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Message-ID: <20100625200203.GF3351@redhat.com>
Date:	Fri, 25 Jun 2010 16:02:03 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	axboe@...nel.dk, linux-kernel@...r.kernel.org,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/3] block: Implement a blk_yield function to voluntarily
 give up the I/O scheduler.

On Fri, Jun 25, 2010 at 12:51:58PM -0400, Jeff Moyer wrote:
> Vivek Goyal <vgoyal@...hat.com> writes:
> 
> > On Tue, Jun 22, 2010 at 05:35:00PM -0400, Jeff Moyer wrote:
> >
> > [..]
> >> @@ -1614,6 +1620,15 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
> >>  	cfq_clear_cfqq_wait_request(cfqq);
> >>  	cfq_clear_cfqq_wait_busy(cfqq);
> >>  
> >> +	if (!cfq_cfqq_yield(cfqq)) {
> >> +		struct cfq_rb_root *st;
> >> +		st = service_tree_for(cfqq->cfqg,
> >> +				      cfqq_prio(cfqq), cfqq_type(cfqq));
> >> +		st->last_expiry = jiffies;
> >> +		st->last_pid = cfqq->pid;
> >> +	}
> >> +	cfq_clear_cfqq_yield(cfqq);
> >
> > Jeff, I think cfqq is still on service tree at this point of time. If yes,
> > then we can simply use cfqq->service_tree, instead of calling
> > service_tree_for().
> 
> Yup.
> 
> > No clearing of cfqq->yield_to field?
> 
> Nope.  Again, it's not required, but if you really want me to, I'll add
> it.

I think clearing up is better as it leaves no scope for confusion.

Thanks
Vivek
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