linux-kernel - Re: [PATCH 1/2] cfq: always return false from should_idle if slice

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Message-ID: <x498w5zdm38.fsf@segfault.boston.devel.redhat.com>
Date:	Mon, 28 Jun 2010 14:54:35 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Jens Axboe <axboe@...nel.dk>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] cfq: always return false from should_idle if slice_idle is set to zero

Jens Axboe <axboe@...nel.dk> writes:

> On 28/06/10 20.41, Jeff Moyer wrote:
>> Jens Axboe <axboe@...nel.dk> writes:
>> 
>>> On 21/06/10 21.49, Jeff Moyer wrote:
>>>> Hi,
>>>>
>>>> In testing a competing fsync-ing process and a sequential reader on
>>>> mid-grade storage, I found that cfq was incapable of achieving the I/O
>>>> rates of deadline, no matter how it was tuned.  Investigation, and insight
>>>> from Vivek (mostly the latter), led to identifying that we were still
>>>> idling for the last queue in the service tree.
>>>>
>>>> Modifying cfq_should_idle to not idle when slice_idle is set to zero got
>>>> us much closer to the performance of deadline for this workload.  I have
>>>> one follow-on patch that gets us on-par with deadline, but I think this
>>>> patch stands alone.
>>>>
>>>> Comments, as always, are appreciated.
>>>
>>> This looks good.
>> 
>> So.... applied to which branch?
>
> Not applied yet, unless I explicitly say it's applied, then it's not
> necessarily in any public git tree yet. But this will go into .35.

OK, thanks for the clarification.

Cheers,
Jeff
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