From: Zhao Yakui <yakui.zhao@xxxxxxxxx> "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@xxxxxxxxx> Signed-off-by: Li Shaohua <shaohua.li@xxxxxxxxx> Signed-off-by: Len Brown <len.brown@xxxxxxxxx> --- Documentation/kernel-parameters.txt | 3 ++- arch/ia64/kernel/process.c | 2 ++ arch/x86/kernel/process.c | 11 +++++++++++ drivers/acpi/processor_core.c | 13 +++++++++++++ drivers/acpi/processor_idle.c | 6 +++++- include/asm-ia64/processor.h | 1 + include/asm-x86/processor.h | 1 + 7 files changed, 35 insertions(+), 2 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index bf8b527..c657339 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -785,7 +785,7 @@ and is between 256 and 4096 characters. It is defined in the file See Documentation/ide/ide.txt. idle= [X86] - Format: idle=poll or idle=mwait, idle=halt + Format: idle=poll or idle=mwait, idle=halt, idle=nomwait Poll forces a polling idle loop that can slightly improves the performance of waking up a idle CPU, but will use a lot of power and make the system run hot. Not recommended. @@ -795,6 +795,7 @@ and is between 256 and 4096 characters. It is defined in the file as idle=poll. idle=halt. Halt is forced to be used for CPU idle. In such case C2/C3 won't be used again. + idle=nomwait. Disable mwait for CPU C-states ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem Claim all unknown PCI IDE storage controllers. diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c index 216e395..4d5edae 100644 --- a/arch/ia64/kernel/process.c +++ b/arch/ia64/kernel/process.c @@ -57,6 +57,8 @@ unsigned long boot_option_idle_override = 0; EXPORT_SYMBOL(boot_option_idle_override); unsigned long idle_halt; EXPORT_SYMBOL(idle_halt); +unsigned long idle_nomwait; +EXPORT_SYMBOL(idle_nomwait); void ia64_do_show_stack (struct unw_frame_info *info, void *arg) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 2b38ec8..3a4a99d 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -10,6 +10,8 @@ unsigned long idle_halt; EXPORT_SYMBOL(idle_halt); +unsigned long idle_nomwait; +EXPORT_SYMBOL(idle_nomwait); struct kmem_cache *task_xstate_cachep; @@ -184,6 +186,15 @@ 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; diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c index 9dd0fa9..eb99e18 100644 --- a/drivers/acpi/processor_core.c +++ b/drivers/acpi/processor_core.c @@ -265,7 +265,20 @@ static int acpi_processor_set_pdc(struct acpi_processor *pr) if (!pdc_in) return status; + if (idle_nomwait) { + /* + * If mwait is disabled for CPU C-states, the C2C3_FFH access + * mode will be disabled in the parameter of _PDC object. + * Of course C1_FFH access mode will also be disabled. + */ + union acpi_object *obj; + u32 *buffer = NULL; + obj = pdc_in->pointer; + buffer = (u32 *)(obj->buffer.pointer); + buffer[2] &= ~(ACPI_PDC_C_C2C3_FFH | ACPI_PDC_C_C1_FFH); + + } status = acpi_evaluate_object(pr->handle, "_PDC", pdc_in, NULL); if (ACPI_FAILURE(status)) diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index a6edf84..2517b1e 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -957,13 +957,17 @@ static int acpi_processor_get_power_info_cst(struct acpi_processor *pr) } else { continue; } - if (cx.type == ACPI_STATE_C1 && idle_halt) { + if (cx.type == ACPI_STATE_C1 && + (idle_halt || idle_nomwait)) { /* * In most cases the C1 space_id obtained from * _CST object is FIXED_HARDWARE access mode. * But when the option of idle=halt is added, * the entry_method type should be changed from * CSTATE_FFH to CSTATE_HALT. + * When the option of idle=nomwait is added, + * the C1 entry_method type should be + * CSTATE_HALT. */ cx.entry_method = ACPI_CSTATE_HALT; snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT"); diff --git a/include/asm-ia64/processor.h b/include/asm-ia64/processor.h index f36e28a..f88fa05 100644 --- a/include/asm-ia64/processor.h +++ b/include/asm-ia64/processor.h @@ -764,6 +764,7 @@ prefetchw (const void *x) extern unsigned long boot_option_idle_override; extern unsigned long idle_halt; +extern unsigned long idle_nomwait; #endif /* !__ASSEMBLY__ */ diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h index 3ee8687..3830854 100644 --- a/include/asm-x86/processor.h +++ b/include/asm-x86/processor.h @@ -733,6 +733,7 @@ extern void select_idle_routine(const struct cpuinfo_x86 *c); extern unsigned long boot_option_idle_override; extern unsigned long idle_halt; +extern unsigned long idle_nomwait; extern void enable_sep_cpu(void); extern int sysenter_setup(void); -- 1.5.6.1.89.gd544 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
