Messages in this thread Patch in this message | | | Date | Wed, 14 May 2008 08:56:05 +0200 | From | Ingo Molnar <> | Subject | Re: [BISECTED] Lots of "rescheduling IPIs" in powertop |
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* Vegard Nossum <vegard.nossum@gmail.com> wrote:
> Hi, > > Recap: powertop shows between 200-400 wakeups/second with the > description "<kernel IPI>: Rescheduling interrupts" when all > processors have load (e.g. I need to run two busy-loops on my 2-CPU > system for this to show up).
ok, could you try the fix below? It was a mistake to make mwait use dependent on power considerations - on a desktop CPU it is unlikely to use more power than a simple HLT - and the IPIs are extra scheduling latency and extra power used.
Ingo
--------------> Subject: x86: remove mwait C-state capability From: Ingo Molnar <mingo@elte.hu> Date: Wed May 14 08:47:40 CEST 2008
Signed-off-by: Ingo Molnar <mingo@elte.hu> --- arch/x86/kernel/process.c | 11 +---------- 1 file changed, 1 insertion(+), 10 deletions(-)
Index: linux/arch/x86/kernel/process.c =================================================================== --- linux.orig/arch/x86/kernel/process.c +++ linux/arch/x86/kernel/process.c @@ -99,15 +99,6 @@ static void mwait_idle(void) local_irq_enable(); } - -static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c) -{ - if (force_mwait) - return 1; - /* Any C1 states supported? */ - return c->cpuid_level >= 5 && ((cpuid_edx(5) >> 4) & 0xf) > 0; -} - /* * On SMP it's slightly faster (but much more power-consuming!) * to poll the ->work.need_resched flag instead of waiting for the @@ -131,7 +122,7 @@ void __cpuinit select_idle_routine(const " performance may degrade.\n"); } #endif - if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) { + if (cpu_has(c, X86_FEATURE_MWAIT)) { /* * Skip, if setup has overridden idle. * One CPU supports mwait => All CPUs supports mwait
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