linux-kernel - Re: aim7 -30% regression in 2.6.24-rc1

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Message-ID: <20071101085824.GA12721@elte.hu>
Date:	Thu, 1 Nov 2007 09:58:24 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: aim7 -30% regression in 2.6.24-rc1


* Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

>  static int one_hundred = 100;
> +static int int_max = INT_MAX;
>  
>  /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
>  static int maxolduid = 65535;
> @@ -239,7 +240,10 @@ static struct ctl_table kern_table[] = {
>  		.data		= &sysctl_sched_nr_latency,
>  		.maxlen		= sizeof(unsigned int),
>  		.mode		= 0644,
> -		.proc_handler	= &proc_dointvec,
> +		.proc_handler	= &proc_dointvec_minmax,
> +		.strategy	= &sysctl_intvec,
> +		.extra1		= &one,
> +		.extra2		= &int_max,

could we instead justmake sched_nr_latency non-tunable, and recalculate 
it from the sysctl handler whenever sched_latency or 
sched_min_granularity changes? That would avoid not only the division by 
zero bug but also other out-of-spec tunings.

	Ingo
-
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