2.6.25-stable review patch. If anyone has any objections, please let us
know.
------------------
From: Ingo Molnar <mingo@elte.hu>
back-ported from upstream commit a738d897b7b03b83488ae74a9bc03d26a2875dc6 by Vegard Nossum
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 0c07ee38c9d4eb081758f5ad14bbffa7197e1aec
| 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: Vegard Nossum <vegard.nossum@gmail.com>
Tested-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
arch/x86/kernel/process_32.c | 10 +---------
arch/x86/kernel/process_64.c | 11 +----------
2 files changed, 2 insertions(+), 19 deletions(-)
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -259,14 +259,6 @@ static void mwait_idle(void)
mwait_idle_with_hints(0, 0);
}
-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;
-}
-
void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
{
static int selected;
@@ -279,7 +271,7 @@ 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
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -254,15 +254,6 @@ static void mwait_idle(void)
}
}
-
-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;
-}
-
void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
{
static int selected;
@@ -275,7 +266,7 @@ 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
--
--
