linux-kernel - Re: [tip:sched/core] sched: Fix capacity calculations for SMT4

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Date:	Thu, 10 Jun 2010 08:48:56 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Michael Neuling <mikey@...ling.org>
Cc:	mingo@...hat.com, hpa@...or.com, vatsa@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, arjan@...ux.intel.com,
	tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/core] sched: Fix capacity calculations for SMT4

On Thu, 2010-06-10 at 09:03 +1000, Michael Neuling wrote:
> Peter,
> 
> It looks like when this was pushed to Ingo, some of the logic was
> changed.  rt_freq_influence() became fix_small_capacity() but the return
> values for these two functions are opposite (return 1 => return 0 and
> visa versa]]).
> 
> This was changed in the sibling test (return 1 => return 0), but the
> check for the change in cpu power due to freq and rt was not.
> 
> So either the return values need to be changed at the end of
> fix_small_capacity() or the cpu_power test needs to be the other way
> around.  Below changes the cpu_power test as it brings it more inline
> with the comment above it.
> 
> Without this the asymmetric packing doesn't work.

D'oh fully my fault for cleaning up.

Thanks, I'll make sure it gets fixed.

> Subject: sched: fix the CPU power test for fix_small_capacity
> 
> The CPU power test is the wrong way around in fix_small_capacity.
> 
> This was due to a small changes made in the posted patch on lkml to what
> was was taken upstream.
> 
> This patch fixes asymmetric packing for POWER7.
> 
> Signed-off-by: Michael Neuling <mikey@...ling.org>
> 
> Index: linux-2.6-ozlabs/kernel/sched_fair.c
> ===================================================================
> --- linux-2.6-ozlabs.orig/kernel/sched_fair.c
> +++ linux-2.6-ozlabs/kernel/sched_fair.c
> @@ -2354,7 +2354,7 @@ fix_small_capacity(struct sched_domain *
>  	/*
>  	 * If ~90% of the cpu_power is still there, we're good.
>  	 */
> -	if (group->cpu_power * 32 < group->cpu_power_orig * 29)
> +	if (group->cpu_power * 32 > group->cpu_power_orig * 29)
>  		return 1;
>  
>  	return 0;
> 

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