linux-kernel - Re: [PATCH 2/2]block cfq: compensate preempted queue even if it has no slice assigned

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Date:	Tue, 18 Jan 2011 08:47:28 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Jens Axboe <jaxboe@...ionio.com>,
	"jmoyer@...hat.com" <jmoyer@...hat.com>,
	Corrado Zoccolo <czoccolo@...il.com>,
	Gui Jianfeng <guijianfeng@...fujitsu.com>
Subject: Re: [PATCH 2/2]block cfq: compensate preempted queue even if it
 has no slice assigned

On Mon, 2011-01-17 at 22:06 +0800, Vivek Goyal wrote:
> On Tue, Jan 11, 2011 at 04:51:57PM +0800, Shaohua Li wrote:
> > If a queue is preempted before it gets slice assigned, the queue doesn't get
> > compensation, which looks unfair. For such queue, we compensate it for a whole
> > slice.
> > 
> > Signed-off-by: Shaohua Li <shaohua.li@...el.com>
> > 
> > ---
> >  block/cfq-iosched.c |   19 +++++++++++++++----
> >  1 file changed, 15 insertions(+), 4 deletions(-)
> > 
> > Index: linux/block/cfq-iosched.c
> > ===================================================================
> > --- linux.orig/block/cfq-iosched.c	2011-01-10 15:37:33.000000000 +0800
> > +++ linux/block/cfq-iosched.c	2011-01-10 15:54:28.000000000 +0800
> > @@ -605,8 +605,8 @@ cfq_group_slice(struct cfq_data *cfqd, s
> >  	return cfq_target_latency * cfqg->weight / st->total_weight;
> >  }
> >  
> > -static inline void
> > -cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
> > +static inline unsigned
> > +cfq_scaled_group_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
> >  {
> 
> Shaohua,
> 
> Above name "cfq_scaled_group_slice()" does not seem appropriate. It sounds
> as if we are calculating scaled group slice length but the fact is we
> are trying to come up with slice length of cfqq. So a better name might
> be cfq_scaled_slice_cfqq() or cfqq_scaled_slice() something like that. 
either is ok to me. can you post a patch to fix it, as the patch is
already merged.

Thanks,
Shaohua

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