linux-kernel - Re: [patchlet] sched: fix rt throttle runtime borrowing

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Message-ID: <AANLkTinToHNbC_Yu91GfzcSTDrzSFFb87qQDGJ1vj4sV@mail.gmail.com>
Date:	Tue, 8 Mar 2011 16:23:28 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Mike Galbraith <efault@....de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [patchlet] sched: fix rt throttle runtime borrowing

On Mon, Mar 7, 2011 at 10:27 PM, Mike Galbraith <efault@....de> wrote:
> sched: fix rt throttle runtime borrowing
>
> If allowed to borrow up to rt_period, the throttle has no effect on an out
> of control RT task, allowing it to consume 100% CPU indefinitely, blocking
> system critical SCHED_NORMAL threads indefinitely.
>
> To make the throttle a more effective safety mechanism, disable borrowing
> by default. while providing an opt-in switch for those who know the risks.
> Also fix the throttle such that it never silently bumps rt_runtime to the
> point that it disables itself (rt_runtime >= rt_period).
>
> Convert balance_runtime() and do_balance_runtime() to void since their
> return values are never used.
>
> Signed-off-by: Mike Galbraith <efault@....de>
>
> ---
> Index: linux-2.6/include/linux/sched.h
> ===================================================================
> --- linux-2.6.orig/include/linux/sched.h
> +++ linux-2.6/include/linux/sched.h
> @@ -1941,6 +1941,7 @@ static inline unsigned int get_sysctl_ti
>  #endif
>  extern unsigned int sysctl_sched_rt_period;
>  extern int sysctl_sched_rt_runtime;
> +extern int sysctl_sched_rt_borrow_runtime;

It should be under CONFIG_SMP.

Thanks,
Yong


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