diff options
author | Zhao Yakui <yakui.zhao@intel.com> | 2008-06-24 06:01:09 -0400 |
---|---|---|
committer | Andi Kleen <andi@basil.nowhere.org> | 2008-07-16 17:27:05 -0400 |
commit | da5e09a1b3e5a9fc0b15a3feb64e921ccc55ba74 (patch) | |
tree | 382a75c1180e458df826ef4efbc191f3f71275c1 /arch/x86/kernel | |
parent | c1e3b377ad48febba6f91b8ae42c44ee4d4ab45e (diff) |
ACPI : Create "idle=nomwait" bootparam
"idle=nomwait" disables the use of the MWAIT
instruction from both C1 (C1_FFH) and deeper (C2C3_FFH)
C-states.
When MWAIT is unavailable, the BIOS and OS generally
negotiate to use the HALT instruction for C1,
and use IO accesses for deeper C-states.
This option is useful for power and performance
comparisons, and also to work around BIOS bugs
where broken MWAIT support is advertised.
http://bugzilla.kernel.org/show_bug.cgi?id=10807
http://bugzilla.kernel.org/show_bug.cgi?id=10914
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Li Shaohua <shaohua.li@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r-- | arch/x86/kernel/process.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 7fc729498760..4d629c62f4f8 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c | |||
@@ -11,6 +11,8 @@ | |||
11 | 11 | ||
12 | unsigned long idle_halt; | 12 | unsigned long idle_halt; |
13 | EXPORT_SYMBOL(idle_halt); | 13 | EXPORT_SYMBOL(idle_halt); |
14 | unsigned long idle_nomwait; | ||
15 | EXPORT_SYMBOL(idle_nomwait); | ||
14 | 16 | ||
15 | struct kmem_cache *task_xstate_cachep; | 17 | struct kmem_cache *task_xstate_cachep; |
16 | 18 | ||
@@ -340,6 +342,15 @@ static int __init idle_setup(char *str) | |||
340 | pm_idle = default_idle; | 342 | pm_idle = default_idle; |
341 | idle_halt = 1; | 343 | idle_halt = 1; |
342 | return 0; | 344 | return 0; |
345 | } else if (!strcmp(str, "nomwait")) { | ||
346 | /* | ||
347 | * If the boot option of "idle=nomwait" is added, | ||
348 | * it means that mwait will be disabled for CPU C2/C3 | ||
349 | * states. In such case it won't touch the variable | ||
350 | * of boot_option_idle_override. | ||
351 | */ | ||
352 | idle_nomwait = 1; | ||
353 | return 0; | ||
343 | } else | 354 | } else |
344 | return -1; | 355 | return -1; |
345 | 356 | ||