linux-kernel - Re: [PATCH V2 0/8] cpusets: Isolate CPUs via sysfs using cpusets

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Message-ID: <CAKohpomW3jpQEqFxD3m_br8GchJyq9-KSxW2x7JLCRqDgf4SAg@mail.gmail.com>
Date:	Mon, 7 Apr 2014 09:41:14 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, Tejun Heo <tj@...nel.org>,
	Li Zefan <lizefan@...wei.com>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Linaro Networking <linaro-networking@...aro.org>,
	Arvind Chauhan <Arvind.Chauhan@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>
Subject: Re: [PATCH V2 0/8] cpusets: Isolate CPUs via sysfs using cpusets

Hi Mike,

On 6 April 2014 14:00, Mike Galbraith <umgwanakikbuti@...il.com> wrote:
> I wonder if adding a quiesce switch is really necessary.
>
> Seems to me that if you don't have load balancing turned off, you can't
> be very concerned about perturbation, so this should be tied into the
> load balancing on/off switch as an extension to isolating cores from the
> #1 perturbation source, the scheduler.

Its more about not doing any background activities on these CPU which can
be avoided. So, even if a add_timer() is issued from these isolated CPUs, it
should goto the set chosen for doing background activity, unless add_timer_on()
has been issued, in which case user wants that code to execute on the
isolated core.

Probably, yes, people would be disabling load_balancing between these
cpusets to avoid migration of tasks to isolated core as well.. Atleast we
are using it :)

> I also didn't notice a check for is_cpu_exclusive() at a glance, which
> would be a bug, but one that would go away if this additional isolation
> were coupled to the existing isolation switch.

Yeah, there is no check for that. But I didn't got your point completely.
Why do I need to check for exclusivity on the isolated CPUs? So, that
same CPU isn't isolated as well as non-isolated on two separate sets?

Thanks for your feedback.

--
viresh
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