Re: ext2/3 performance regression in 2.6 vs 2.4 for small interl

[Nick Piggin]

Jamie Lokier wrote:

> Helge Hafting wrote:
>
> > Something similiar could be done for io niceness.  If we run out of
> > normal priority io, how about not issuing the low priority io
> > right away.  Anticipate there will be more high-priority io
> > and wait for some idle time before letting low-priority
> > requests through.  And of course some maximum wait to prevent
> > total starvation.
>
> The problem is quite similar to scheduling for quality on a network
> device.  Once a packet has started going it, usually you cannot abort
> the packet for a higher priority one.
>
> I thought there was a CBQ I/O scheduling patch or such to offer some
> kind of I/O niceness these days?

Yeah its Jens' CFQ io scheduler. It is in -mm, and I think it
has adjustable priorities now.

I have plans to do IO priorities in the anticipatory scheduler
(significantly differently to CFQ). One day...

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