linux-kernel - Re: Do we support ioprio on SSDs with NCQ (Was: Re: IO scheduler based IO controller V10)

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Message-ID: <20091006084120.GJ5216@kernel.dk>
Date:	Tue, 6 Oct 2009 10:41:20 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Corrado Zoccolo <czoccolo@...il.com>
Cc:	Jeff Moyer <jmoyer@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
	Valdis.Kletnieks@...edu, Mike Galbraith <efault@....de>,
	Ingo Molnar <mingo@...e.hu>,
	Ulrich Lukas <stellplatz-nr.13a@...enparkplatz.de>,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, dm-devel@...hat.com,
	nauman@...gle.com, dpshah@...gle.com, lizf@...fujitsu.com,
	mikew@...gle.com, fchecconi@...il.com, paolo.valente@...more.it,
	ryov@...inux.co.jp, fernando@....ntt.co.jp,
	dhaval@...ux.vnet.ibm.com, balbir@...ux.vnet.ibm.com,
	righi.andrea@...il.com, m-ikeda@...jp.nec.com, agk@...hat.com,
	akpm@...ux-foundation.org, peterz@...radead.org,
	jmarchan@...hat.com, torvalds@...ux-foundation.org, riel@...hat.com
Subject: Re: Do we support ioprio on SSDs with NCQ (Was: Re: IO scheduler
	based IO controller V10)

On Mon, Oct 05 2009, Corrado Zoccolo wrote:
> On Mon, Oct 5, 2009 at 5:06 PM, Jeff Moyer <jmoyer@...hat.com> wrote:
> > Corrado Zoccolo <czoccolo@...il.com> writes:
> >
> >> Moreover, I suggest removing also the slice_resid part, since its
> >> semantics doesn't seem consistent.
> >> When computed, it is not the residency, but the remaining time slice.
> >
> > It stands for residual, not residency.  Make more sense?
> It makes sense when computed, but not when used in rb_key computation.
> Why should we postpone queues that where preempted, instead of giving
> them a boost?

We should not, if it is/was working correctly, it should allow both for
increase/descrease of tree position (hence it's a long and can go
negative) to account for both over and under time.

-- 
Jens Axboe

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