linux-kernel - Re: [ANNOUNCE] Linsched for 2.6.35 released

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Message-ID: <AANLkTikFXGW7iJX+S6NNj-wT15mUXKx21fEP1+9nKkv6@mail.gmail.com>
Date:	Tue, 15 Feb 2011 10:25:18 -0800
From:	Ranjit Manomohan <ranjitm@...gle.com>
To:	svaidy@...ux.vnet.ibm.com
Cc:	linux-kernel@...r.kernel.org, Mike Galbraith <efault@....de>,
	Nikhil Rao <ncrao@...gle.com>, Salman Qazi <sqazi@...gle.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Paul Turner <pjt@...gle.com>
Subject: Re: [ANNOUNCE] Linsched for 2.6.35 released

On Tue, Feb 8, 2011 at 10:10 AM, Vaidyanathan Srinivasan
<svaidy@...ux.vnet.ibm.com> wrote:
> * Ranjit Manomohan <ranjitm@...gle.com> [2010-11-15 17:52:05]:
>
>> On Mon, Oct 18, 2010 at 9:52 PM, Vaidyanathan Srinivasan
>> <svaidy@...ux.vnet.ibm.com> wrote:
>> > * Ranjit Manomohan <ranjitm@...gle.com> [2010-10-12 10:29:54]:
>> >
>
> [snip]
>
>> > Can you help me figure out how to get to kstat_cpu() or per-cpu
>> > kernel_stat accounting/utilisation metrics within the simulation?
>>
>> we don't use the kstat_cpu accounting in the simulation since it does
>> not really make sense in this environment.
>>
>> We have a timer driven loop that advances time globally and kicks of
>> events scheduled to run at specified times on each CPU. The periodic
>> timer tick is one among these events. Since there is really no notion
>> of system vs user time in this scenario, the current code disables the
>> update_process_times routine. I am not sure how these times relate to
>> the task placement logic you are trying to verify. If you could let me
>> know how you plan to use these then I can try to accommodate that in
>> the simulation.
>
> The current setup lets us find how much time each task was run.
> I would like to use the kernel_stat information to understand 'which
> cpu' ran the task.  Basically we could place nr_tasks < nr_cpus and
> see them settle to the right CPUs within the sched domain topology.
> This can be verified by checking the CPU's utilisation or run time at
> the end of the simulation.  Like two tasks on the same socket of
> a dual-socket dual-core system should settle to one task per socket.
> The load balancer should be able to spread the tasks around slowly.
>
> The ability to create diverse topology within linsched is very
> useful to test these load balancer functions and corner cases.

Ok, I understand what you are looking for. There does not seem to be
anything in the kernel that I can reuse. I can add a Linsched specific
per cpu task counter to get the stats. I will try to send out an
update in a couple of days.

>
>> Sorry for the delay in response. My mail filters messed this up.
>
> I got your reply earlier. No problem with the delay.
> Do you have a new version to share?  Any new feature that you are planning?

Unfortunately we have fallen a little behind in terms of keeping
linsched up to date with mainline kernel releases. Hopefully we can
get an updated version out this summer. Our current plans are to
include a record/replay type of option to the simulation that will
allow us to optimize a particular workload. Please let me know if
there is anything else that you would like to see added.

-Thanks,
Ranjit

>
> --Vaidy
>
>
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