Commit a738d897 authored by Ingo Molnar's avatar Ingo Molnar Committed by Thomas Gleixner

x86: remove mwait capability C-state check

Vegard Nossum reports:

| 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).
|
| The bisect resulted in this commit:
|
| commit 0c07ee38
| Date:   Wed Jan 30 13:33:16 2008 +0100
|
|     x86: use the correct cpuid method to detect MWAIT support for C states

remove the functional effects of this patch and make mwait unconditional.

A future patch will turn off mwait on specific CPUs where that causes
power to be wasted.
Bisected-by: default avatarVegard Nossum <vegard.nossum@gmail.com>
Tested-by: default avatarVegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f26a3988
......@@ -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 struct cpuinfo_x86 *c)
" 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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