From: Vincent Guittot <vincent.guittot@linaro.org> To: Arjan van de Ven <arjan@linux.intel.com> Cc: Ingo Molnar <mingo@elte.hu>, Suresh Siddha <suresh.b.siddha@intel.com>, Youquan Song <youquan.song@intel.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-kernel@vger.kernel.org, tglx@linutronix.de, hpa@zytor.com, akpm@linux-foundation.org, stable@vger.kernel.org, len.brown@intel.com, anhua.xu@intel.com, chaohong.guo@intel.com, Youquan Song <youquan.song@linux.intel.com> Subject: Re: [PATCH] x86,sched: Fix sched_smt_power_savings totally broken Date: Tue, 10 Jan 2012 16:32:44 +0100 [thread overview] Message-ID: <CAKfTPtDCSQRbNv38sLNErhFpz=zKNUHcK1WQUeukoT4QfVtAxw@mail.gmail.com> (raw) In-Reply-To: <4F0C4BF0.9090809@linux.intel.com> On 10 January 2012 15:32, Arjan van de Ven <arjan@linux.intel.com> wrote: > On 1/10/2012 1:18 AM, Ingo Molnar wrote: >> >> * Suresh Siddha <suresh.b.siddha@intel.com> wrote: >> >>> On Tue, 2012-01-10 at 00:58 -0500, Youquan Song wrote: >>>> Thanks Peter! Here is the patch. >>> >>> Youquan, As far as I know both the >>> sched_smt_power_savings/sched_mc_power_savings are broken for atleast an >>> year. >> >> We want a single knob, sched_power_savings - with the mc_ and >> smt_ ones still kept and aliased to sched_power_savings, for >> compatibility reasons. >> >> As Peter said, the other reasonable option is to have no knob at >> all and restart this code from scratch. >> >> The other thing we should do is to add sane defaults: to turn on >> sched_power_savings *AUTOMATICALLY* when a system is obviously >> battery driven and turn it off when the system is obviously AC >> driven. User-space can still implement policy and override the >> kernel's default, but there's absolutely no excuse to not offer >> this default ourselves. > > a very good default would be to keep all tasks on one package until half > the cores in the package are busy, and then start spreading out. > The choice of spreading or not tasks is clearly architecture or even platform dependent. Can't we get such optimal threshold information from architecture code ? > I suspect that'll be the 90% case coverage. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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From: Vincent Guittot <vincent.guittot@linaro.org> To: Arjan van de Ven <arjan@linux.intel.com> Cc: Ingo Molnar <mingo@elte.hu>, Suresh Siddha <suresh.b.siddha@intel.com>, Youquan Song <youquan.song@intel.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-kernel@vger.kernel.org, tglx@linutronix.de, hpa@zytor.com, akpm@linux-foundation.org, stable@vger.kernel.org, len.brown@intel.com, anhua.xu@intel.com, chaohong.guo@intel.com, Youquan Song <youquan.song@linux.intel.com> Subject: Re: [PATCH] x86,sched: Fix sched_smt_power_savings totally broken Date: Tue, 10 Jan 2012 16:32:44 +0100 [thread overview] Message-ID: <CAKfTPtDCSQRbNv38sLNErhFpz=zKNUHcK1WQUeukoT4QfVtAxw@mail.gmail.com> (raw) In-Reply-To: <4F0C4BF0.9090809@linux.intel.com> On 10 January 2012 15:32, Arjan van de Ven <arjan@linux.intel.com> wrote: > On 1/10/2012 1:18 AM, Ingo Molnar wrote: >> >> * Suresh Siddha <suresh.b.siddha@intel.com> wrote: >> >>> On Tue, 2012-01-10 at 00:58 -0500, Youquan Song wrote: >>>> Thanks Peter! Here is the patch. >>> >>> Youquan, As far as I know both the >>> sched_smt_power_savings/sched_mc_power_savings are broken for atleast an >>> year. >> >> We want a single knob, sched_power_savings - with the mc_ and >> smt_ ones still kept and aliased to sched_power_savings, for >> compatibility reasons. >> >> As Peter said, the other reasonable option is to have no knob at >> all and restart this code from scratch. >> >> The other thing we should do is to add sane defaults: to turn on >> sched_power_savings *AUTOMATICALLY* when a system is obviously >> battery driven and turn it off when the system is obviously AC >> driven. User-space can still implement policy and override the >> kernel's default, but there's absolutely no excuse to not offer >> this default ourselves. > > a very good default would be to keep all tasks on one package until half > the cores in the package are busy, and then start spreading out. > The choice of spreading or not tasks is clearly architecture or even platform dependent. Can't we get such optimal threshold information from architecture code ? > I suspect that'll be the 90% case coverage. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at �http://vger.kernel.org/majordomo-info.html > Please read the FAQ at �http://www.tux.org/lkml/
next prev parent reply other threads:[~2012-01-10 15:32 UTC|newest] Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-01-09 8:56 [PATCH] x86,sched: Fix sched_smt_power_savings totally broken Youquan Song 2012-01-09 10:06 ` Peter Zijlstra 2012-01-09 10:28 ` Peter Zijlstra 2012-01-09 10:30 ` Peter Zijlstra 2012-01-09 11:00 ` Vaidyanathan Srinivasan 2012-01-09 14:35 ` Peter Zijlstra 2012-01-09 16:03 ` Vaidyanathan Srinivasan 2012-01-09 16:13 ` Peter Zijlstra 2012-01-09 17:05 ` Vaidyanathan Srinivasan 2012-01-09 14:13 ` Arjan van de Ven 2012-05-18 10:19 ` [tip:sched/core] sched: Remove stale power aware scheduling remnants and dysfunctional knobs tip-bot for Peter Zijlstra 2012-01-10 0:14 ` [PATCH] x86,sched: Fix sched_smt_power_savings totally broken Youquan Song 2012-01-09 11:05 ` Peter Zijlstra 2012-01-10 5:58 ` Youquan Song 2012-01-09 23:52 ` Suresh Siddha 2012-01-10 9:18 ` Ingo Molnar 2012-01-10 14:32 ` Arjan van de Ven 2012-01-10 14:41 ` Peter Zijlstra 2012-01-10 14:54 ` Arjan van de Ven 2012-01-10 15:32 ` Vincent Guittot [this message] 2012-01-10 15:32 ` Vincent Guittot 2012-01-10 16:49 ` Vaidyanathan Srinivasan 2012-01-10 19:41 ` Ingo Molnar 2012-01-10 19:44 ` Ingo Molnar 2012-01-10 16:54 ` Youquan Song 2012-01-10 16:51 ` Vaidyanathan Srinivasan 2012-01-10 19:01 ` Suresh Siddha 2012-01-11 3:52 ` Vaidyanathan Srinivasan 2012-01-11 17:37 ` Youquan Song 2012-01-10 16:44 ` Vaidyanathan Srinivasan 2012-01-09 11:12 ` Peter Zijlstra 2012-01-09 14:29 ` Vincent Guittot 2012-01-09 14:29 ` Vincent Guittot 2012-01-09 14:46 ` Peter Zijlstra 2012-01-10 2:12 ` Indan Zupancic 2012-01-10 9:26 ` Peter Zijlstra 2012-01-10 1:54 ` Suresh Siddha 2012-01-10 8:08 ` Vincent Guittot 2012-01-09 15:37 ` Greg KH
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