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From: Joel Schopp <jschopp@austin.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
	linuxppc-dev@lists.ozlabs.org,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	ego@in.ibm.com
Subject: Re: [PATCHv3 2/2] powerpc: implement arch_scale_smt_power for Power7
Date: Fri, 29 Jan 2010 12:41:38 -0600	[thread overview]
Message-ID: <4B632BE2.9020106@austin.ibm.com> (raw)
In-Reply-To: <1264728185.20211.34.camel@pasglop>

Benjamin Herrenschmidt wrote:
> On Thu, 2010-01-28 at 17:24 -0600, Joel Schopp wrote:
>   
>> On Power7 processors running in SMT4 mode with 2, 3, or 4 idle threads 
>> there is performance benefit to idling the higher numbered threads in
>> the core.  
>>
>> This patch implements arch_scale_smt_power to dynamically update smt
>> thread power in these idle cases in order to prefer threads 0,1 over
>> threads 2,3 within a core.
>>     
>
> Almost there :-) Joel, Peter, can you help me figure something out tho ?
>
> On machine that don't have SMT, I would like to avoid calling
> arch_scale_smt_power() at all if possible (in addition to not compiling
> it in if SMT is not enabled in .config).
>
> Now, I must say I'm utterly confused by how the domains are setup and I
> haven't quite managed to sort it out... it looks to me that
> SD_SHARE_CPUPOWER is always going to be set on all CPUs when the config
> option is set (though each CPU will have its own domain) or am I
> misguided ? IE. Is there any sense in having at least a fast exit path
> out of arch_scale_smt_power() for non-SMT CPUs ?
>
> Joel, can you look at compiling it out when SMT is not set ? We don't
> want to bloat SMP kernels for 32-bit non-SMT embedded platforms.
>   
I can wrap the powerpc definition of arch_scale_smt in an #ifdef, if 
it's not there the scheduler uses the default, which is the same as it 
uses if SMT isn't compiled. 

  parent reply	other threads:[~2010-01-29 18:41 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-01-20 20:00 [PATCH 0/2] sched: arch_scale_smt_powers Joel Schopp
2010-01-20 20:02 ` [PATCH 1/2] sched: Fix the place where group powers are updated Joel Schopp
2010-01-26 23:28   ` [PATCHv2 1/2] sched: enable ARCH_POWER Joel Schopp
2010-01-28 23:20     ` [PATCHv3 " Joel Schopp
2010-02-05 20:57       ` [PATCHv4 " Joel Schopp
2010-01-20 20:04 ` [PATCH 2/2] powerpc: implement arch_scale_smt_power for Power7 Joel Schopp
2010-01-20 20:48   ` Peter Zijlstra
2010-01-20 21:58     ` Michael Neuling
2010-01-20 22:44     ` Joel Schopp
2010-01-21  8:27       ` Peter Zijlstra
2010-01-20 21:04   ` Michael Neuling
2010-01-20 22:09     ` Joel Schopp
2010-01-24  3:00       ` Benjamin Herrenschmidt
2010-01-25 17:50         ` Joel Schopp
2010-01-26  4:23           ` Benjamin Herrenschmidt
2010-01-20 21:33   ` Benjamin Herrenschmidt
2010-01-20 22:36     ` Joel Schopp
2010-01-26 23:28   ` [PATCHv2 " Joel Schopp
2010-01-27  0:52     ` Benjamin Herrenschmidt
2010-01-28 22:39       ` Joel Schopp
2010-01-29  1:23         ` Benjamin Herrenschmidt
2010-01-28 23:20     ` [PATCHv3 " Joel Schopp
2010-01-28 23:24       ` Joel Schopp
2010-01-29  1:23         ` Benjamin Herrenschmidt
2010-01-29 10:13           ` Peter Zijlstra
2010-01-29 18:34             ` Joel Schopp
2010-01-29 18:41           ` Joel Schopp [this message]
2010-02-05 20:57         ` [PATCHv4 " Joel Schopp
2010-02-14 10:12           ` Peter Zijlstra
2010-02-17 22:20             ` Michael Neuling
2010-02-18 13:17               ` Peter Zijlstra
2010-02-18 13:19                 ` Peter Zijlstra
2010-02-18 16:28                 ` Joel Schopp
2010-02-18 17:08                   ` Peter Zijlstra
2010-02-19  6:05                 ` Michael Neuling
2010-02-19 10:01                   ` Peter Zijlstra
2010-02-19 11:01                     ` Michael Neuling
2010-02-23  6:08                       ` Michael Neuling
2010-02-23 16:24                         ` Peter Zijlstra
2010-02-23 16:30                           ` Peter Zijlstra
2010-02-24  6:07                           ` Michael Neuling
2010-02-24 11:13                             ` Michael Neuling
2010-02-24 11:58                               ` Michael Neuling
2010-02-27 10:21                               ` Michael Neuling
2010-03-02 14:44                                 ` Peter Zijlstra
2010-03-04 22:28                                   ` Michael Neuling
2010-01-29 12:25       ` [PATCHv3 " Gabriel Paubert
2010-01-29 16:26         ` Joel Schopp
2010-01-26 23:27 ` [PATCHv2 0/2] sched: arch_scale_smt_powers v2 Joel Schopp
2010-01-28 23:20   ` [PATCHv3 0/2] sched: arch_scale_smt_powers Joel Schopp
2010-02-05 20:57     ` [PATCHv4 " Joel Schopp

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