From: Thomas Renninger <trenn-l3A5Bk7waGM@public.gmane.org>
To: power-072X8lT/F9NAfugRpC6u6w@public.gmane.org
Cc: Peter Clifton <pcjc2-KWPb1pKIrIJaa/9Udqfwiw@public.gmane.org>,
"intel-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org"
<intel-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>
Subject: Re: [Intel-gfx] less load less performance
Date: Tue, 2 Nov 2010 16:53:35 +0100 [thread overview]
Message-ID: <201011021653.35823.trenn@suse.de> (raw)
In-Reply-To: <1288554267.31411.14.camel@zwerg>
On Sunday 31 October 2010 20:44:27 Alexey Fisher wrote:
> Am Sonntag, den 31.10.2010, 20:18 +0100 schrieb Andreas Mohr:
...
> >
> > Why painfully compile a custom c app to keep the CPU busy?
> >
> > Boot with processor.max_cstate=1
> > Much better performance? --> "BUG"!
> > ("BUG" == "something should probably be done about these power management side
> > effects")
>
> for some reasons "processor.max_cstate=1" do not make any difference,
> cpu still use C4.
This is because the new intel_idle driver is used:
cat /sys/devices/system/cpu/cpuidle/current_driver
either you pass both:
intel_idle.max_cstate=0 processor.max_cstate=1
or with the patch I posted today to the linux-acpi list,
idle=halt (C1) idle=poll (busy idling, no power saving at all) can
be used:
[PATCH] intel_idle: Do not load if user overrides idle function via idle= boot param
Hmm, a more generic cpuidle param:
cpuidle.max_state=
may make sense as well.
> Interesting is maxcpus=1 do difference, C4 is used and
> it perform good too.
I am not familiar with the very details of Atoms very deep
C-state implementation, but it could be that all cores/siblings
of a CPU socket need to request sleep states so that C4 or
whatever HW triggered internal power savings take place.
> So what can it be? Some SMP scheduler problem, IRQ
> balancing?
> I know intel CPUs had some PM problem, if 1 core is disabled it consume
> more power (may be no C4?).
Sounds like this is the case...
Thomas
next prev parent reply other threads:[~2010-11-02 15:53 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-31 16:44 less load less performance Alexey Fisher
2010-10-31 17:01 ` Peter Clifton
2010-10-31 17:40 ` Alexey Fisher
2010-10-31 19:18 ` [Intel-gfx] " Andreas Mohr
2010-10-31 19:44 ` Alexey Fisher
2010-11-02 15:53 ` Thomas Renninger [this message]
2010-10-31 17:33 ` Vasily Khoruzhick
2010-10-31 22:07 ` Arjan van de Ven
2010-11-01 8:50 ` Alexey Fisher
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