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Date:	Tue, 27 Oct 2009 13:00:29 +0530
From:	Pankaj Parakh <>
To:	Peter Williams <>
Cc:	Linux Kernel Mailing List <>,
	XingChao Wang <>
Subject: Re: How to add scheduler

On Sat, Oct 24, 2009 at 6:07 AM, Peter Williams <> wrote:
> On 24/10/09 01:10, Pankaj Parakh wrote:
>> Hi Peter,
>> Thanks for showing your interest, I am student and I am working on a
>> project similar to yours i.e. to have a facility where in one can swap
>> scheduler in run-time, but I am in very initial state of learning so I
>> wanted to try a simple RR scheduler, objective of doing it is to learn
>> about different interfaces in modular design(introduced from 2.6.23
>> with CFS). I do not have any constraint with version of linux. I am
>> ready to take part with you provided you do not have any issue.
> No.  That's good.
> I've attached two patches which contain the work I've done so far.  They
> should be applied in the following order:
> define_prelim_cpu_pisch_drv.patch
> implement_spbrr_cpu_pisch_dvr.patch
> and will result in two schedulers: the default CFS 'fair' (cfs_fair)
> scheduler and a simple priority based round robin (spbrr) scheduler; being
> available for selection at boot time and run time.
> To select a scheduler at boot time just add 'cpu_pisch=cfs_fair' or
> 'cpu_pisch=spbrr' to the boot command line.
> To select a scheduler at run time (as root) do:
> echo -n 'cfs_fair' > /sys/kernel/cpu_pisch/name
> or
> echo -n 'spbrr' > /sys/kernel/cpu_pisch/name
> The first step in adding your own scheduler would be to make a copy of the
> file kernel/cpu_pisch_spbrr.c and then modify it.  You will also need to
> modify:
> kernel/sched.c
> kernel/cpu_pisch_drv.c
> kernel/Kconfig.cpu_pisch
> Hopefully, the required changes are obvious.  If not don't hesitate to ask
> questions.  Also if you feel the need to modify the scheduler interface
> (defined in include/linux/cpu_pisch_drv.h) feel free BUT think very
> carefully about it and try not to make things too complex.
> I am working on another scheduler (a simple entitlement based round robin
> (sebrr) scheduler) which I hope to have finished before I publicly release
> the patches.
> If you wish to have your scheduler included just send it to me as a patch
> which applies on top of the ones that I've attached.
> Cheers
> Peter
> --
> Peter Williams                         
> "Learning, n. The kind of ignorance distinguishing the studious."
>  -- Ambrose Bierce

Hi Peter,

To which version of Linux Kernel should I apply the given patch.

Pankaj Parakh
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