linux-kernel - Re: [GIT PULL] scheduler fixes

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Date:	Mon, 4 Apr 2011 08:45:34 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] scheduler fixes

So I pulled this, but I think this:

On Sat, Apr 2, 2011 at 3:31 AM, Ingo Molnar <mingo@...e.hu> wrote:
>
> -               if (interval > HZ*NR_CPUS/10)
> -                       interval = HZ*NR_CPUS/10;
> +               if (interval > HZ*num_online_cpus()/10)
> +                       interval = HZ*num_online_cpus()/10;

is a horrible patch.

Think about what that expands to. It's going to potentially be two
function calls. And the code is just ugly.

So please, when doing search-and-replace changes like this, just clean
up the code at the same time. Back when it was about pure constants,
there was only a typing/ugly overhead from duplicating the constant,
but the compiler would see a single constant.

Now it's _possible_ that the compiler could do the analysis and fold
it all back to a single thing. But it's unlikely to happen except for
configurations that end up making it all trivial.

So just add something like a

   int max_interval = HZ*num_online_cpus()/10;

possibly even with a comment about _why_ that is the max interval allowed.  Ok?

                        Linus
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