linux-kernel - Re: [PATCH 15/15] x86: Fix cpu_coregroup_mask to return correct cpumask on multi-node processors

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Date:	Tue, 25 Aug 2009 11:31:01 +0200
From:	Andreas Herrmann <andreas.herrmann3@....com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/15] x86: Fix cpu_coregroup_mask to return correct
	cpumask on multi-node processors

On Mon, Aug 24, 2009 at 05:36:16PM +0200, Peter Zijlstra wrote:
> On Thu, 2009-08-20 at 15:46 +0200, Andreas Herrmann wrote:
> > The correct mask that describes core-siblings of an processor
> > is topology_core_cpumask. See topology adapation patches, especially
> > http://marc.info/?l=linux-kernel&m=124964999608179
> 
> 
> argh, violence, murder kill.. this is the worst possible hack and you're
> extending it :/

So this is the third code area
(besides sched_*_power_savings sysfs interface, and the __cpu_power fiddling)
that is crap, mess, a hack.

Didn't know that I'd enter such a minefield when touching this code. ;-(

What would be your perferred solution for the
core_cpumask/llc_shared_map stuff?  Another domain level to get rid of
this function?

> > Signed-off-by: Andreas Herrmann <andreas.herrmann3@....com>
> > ---
> >  arch/x86/kernel/smpboot.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> > index f797214..f39bb2c 100644
> > --- a/arch/x86/kernel/smpboot.c
> > +++ b/arch/x86/kernel/smpboot.c
> > @@ -446,7 +446,7 @@ const struct cpumask *cpu_coregroup_mask(int cpu)
> >  	 * And for power savings, we return cpu_core_map
> >  	 */
> >  	if (sched_mc_power_savings || sched_smt_power_savings)
> > -		return cpu_core_mask(cpu);
> > +		return topology_core_cpumask(cpu);
> >  	else
> >  		return c->llc_shared_map;
> >  }
> 

Andreas

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