Re: [PATCH 02/20] blkio: Change CFQ to use CFS like queue timestamps

From: Vivek Goyal
Date: Wed Nov 04 2009 - 18:22:45 EST

On Wed, Nov 04, 2009 at 10:18:15PM +0100, Corrado Zoccolo wrote:
> Hi Vivek,
> On Wed, Nov 4, 2009 at 12:43 AM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
> > o Previously CFQ had one service tree where queues of all theree prio classes
> >  were being queued. One side affect of this time stamping approach is that
> >  now single tree approach might not work and we need to keep separate service
> >  trees for three prio classes.
> >
> Single service tree is no longer true in cfq for-2.6.33.
> Now we have a matrix of service trees, with first dimension being the
> priority class, and second dimension being the workload type
> (synchronous idle, synchronous no-idle, async).
> You can have a look at the series: .
> It may have other interesting influences on your work, as the idle
> introduced at the end of the synchronous no-idle tree, that provides
> fairness also for seeky or high-think-time queues.

Hi Corrado,

Had one more question. Now with dynamic slice length (reduce slice length
to meet target latency), don't wee see reduced throughput on rotational
media with sequential workload?

I saw some you posted numbers for SSD. Do you have some numbers for
rotational media also?

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