From da5e09a1b3e5a9fc0b15a3feb64e921ccc55ba74 Mon Sep 17 00:00:00 2001 From: Zhao Yakui Date: Tue, 24 Jun 2008 18:01:09 +0800 Subject: 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 Signed-off-by: Li Shaohua Signed-off-by: Len Brown Signed-off-by: Andi Kleen --- arch/x86/kernel/process.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'arch/x86') diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 7fc72949876..4d629c62f4f 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -11,6 +11,8 @@ unsigned long idle_halt; EXPORT_SYMBOL(idle_halt); +unsigned long idle_nomwait; +EXPORT_SYMBOL(idle_nomwait); struct kmem_cache *task_xstate_cachep; @@ -340,6 +342,15 @@ static int __init idle_setup(char *str) pm_idle = default_idle; idle_halt = 1; return 0; + } else if (!strcmp(str, "nomwait")) { + /* + * If the boot option of "idle=nomwait" is added, + * it means that mwait will be disabled for CPU C2/C3 + * states. In such case it won't touch the variable + * of boot_option_idle_override. + */ + idle_nomwait = 1; + return 0; } else return -1; -- cgit v1.2.3