linux-kernel - Re: BUG: sched_mc_powersavings broken on pre-Nehalem x86 platforms

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Message-ID: <20100208124649.GE2931@dirshya.in.ibm.com>
Date:	Mon, 8 Feb 2010 18:16:49 +0530
From:	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Ingo Molnar <mingo@...e.hu>, Gautham R Shenoy <ego@...ibm.com>,
	Arun Bharadwaj <arun@...ux.vnet.ibm.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: BUG: sched_mc_powersavings broken on pre-Nehalem x86 platforms

* Peter Zijlstra <peterz@...radead.org> [2010-02-08 12:35:48]:

> On Mon, 2010-02-08 at 15:35 +0530, Vaidyanathan Srinivasan wrote:
> 
> >     Fix for sched_mc_powersavigs for pre-Nehalem platforms.
> >     Child sched domain should clear SD_PREFER_SIBLING if parent will have 
> >     SD_POWERSAVINGS_BALANCE because they are contradicting.
> > 
> >     Sets the flags correctly based on sched_mc_power_savings.
> >     
> >     Signed-off-by: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
> > 
> > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > index 6550415..ef6b7cd 100644
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -866,7 +866,10 @@ static inline int sd_balance_for_mc_power(void)
> >  	if (sched_smt_power_savings)
> >  		return SD_POWERSAVINGS_BALANCE;
> >  
> > -	return SD_PREFER_SIBLING;
> > +	if (!sched_mc_power_savings)
> > +		return SD_PREFER_SIBLING;
> > +
> > +	return 0;
> >  }
> >  
> >  static inline int sd_balance_for_package_power(void)
> > 
> 
> Looks good, thanks!
> 
> What's the status of getting rid of sched_{mc,smt}_power_savings?

Hi Peter,

With the current rearrangement of the code, the unified
sched_power_savings seems more doable.

However, I have few more fixes for sched_smt_powersavings on Nehalem
before I would revisit the unified tunable.

--Vaidy

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