Re: [PATCH 1/2] cfq: always return false from should_idle if slice_idleis set to zero

From: Jens Axboe
Date: Mon Jun 28 2010 - 14:50:50 EST

On 28/06/10 20.41, Jeff Moyer wrote:
> Jens Axboe <axboe@xxxxxxxxx> 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.

Jens Axboe

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