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x86 idle: remove mwait_idle() and "idle=mwait" cmdline param
mwait_idle() is a C1-only idle loop intended to be more efficient than HLT, starting on Pentium-4 HT-enabled processors. But mwait_idle() has been replaced by the more general mwait_idle_with_hints(), which handles both C1 and deeper C-states. ACPI processor_idle and intel_idle use only mwait_idle_with_hints(), and no longer use mwait_idle(). Here we simplify the x86 native idle code by removing mwait_idle(), and the "idle=mwait" bootparam used to invoke it. Since Linux 3.0 there has been a boot-time warning when "idle=mwait" was invoked saying it would be removed in 2012. This removal was also noted in the (now removed:-) feature-removal-schedule.txt. After this change, kernels configured with (CONFIG_ACPI=n && CONFIG_INTEL_IDLE=n) when run on hardware that supports MWAIT will simply use HLT. If MWAIT is desired on those systems, cpuidle and the cpuidle drivers above can be enabled. Signed-off-by: Len Brown <len.brown@intel.com> Cc: x86@kernel.org
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@ -1039,16 +1039,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
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Claim all unknown PCI IDE storage controllers.
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Claim all unknown PCI IDE storage controllers.
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idle= [X86]
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idle= [X86]
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Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
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Format: idle=poll, idle=halt, idle=nomwait
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Poll forces a polling idle loop that can slightly
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Poll forces a polling idle loop that can slightly
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improve the performance of waking up a idle CPU, but
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improve the performance of waking up a idle CPU, but
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will use a lot of power and make the system run hot.
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will use a lot of power and make the system run hot.
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Not recommended.
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Not recommended.
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idle=mwait: On systems which support MONITOR/MWAIT but
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the kernel chose to not use it because it doesn't save
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as much power as a normal idle loop, use the
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MONITOR/MWAIT idle loop anyways. Performance should be
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the same as idle=poll.
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idle=halt: Halt is forced to be used for CPU idle.
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idle=halt: Halt is forced to be used for CPU idle.
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In such case C2/C3 won't be used again.
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In such case C2/C3 won't be used again.
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idle=nomwait: Disable mwait for CPU C-states
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idle=nomwait: Disable mwait for CPU C-states
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@ -725,7 +725,7 @@ extern unsigned long boot_option_idle_override;
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extern bool amd_e400_c1e_detected;
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extern bool amd_e400_c1e_detected;
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enum idle_boot_override {IDLE_NO_OVERRIDE=0, IDLE_HALT, IDLE_NOMWAIT,
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enum idle_boot_override {IDLE_NO_OVERRIDE=0, IDLE_HALT, IDLE_NOMWAIT,
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IDLE_POLL, IDLE_FORCE_MWAIT};
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IDLE_POLL};
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extern void enable_sep_cpu(void);
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extern void enable_sep_cpu(void);
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extern int sysenter_setup(void);
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extern int sysenter_setup(void);
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@ -421,27 +421,6 @@ void stop_this_cpu(void *dummy)
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}
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}
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}
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}
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/* Default MONITOR/MWAIT with no hints, used for default C1 state */
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static void mwait_idle(void)
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{
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if (!need_resched()) {
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trace_power_start_rcuidle(POWER_CSTATE, 1, smp_processor_id());
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trace_cpu_idle_rcuidle(1, smp_processor_id());
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if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
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clflush((void *)¤t_thread_info()->flags);
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__monitor((void *)¤t_thread_info()->flags, 0, 0);
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smp_mb();
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if (!need_resched())
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__sti_mwait(0, 0);
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else
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local_irq_enable();
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trace_power_end_rcuidle(smp_processor_id());
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trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
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} else
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local_irq_enable();
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}
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/*
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/*
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* On SMP it's slightly faster (but much more power-consuming!)
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* On SMP it's slightly faster (but much more power-consuming!)
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* to poll the ->work.need_resched flag instead of waiting for the
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* to poll the ->work.need_resched flag instead of waiting for the
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@ -458,53 +437,6 @@ static void poll_idle(void)
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trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
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trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
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}
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}
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/*
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* mwait selection logic:
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*
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* It depends on the CPU. For AMD CPUs that support MWAIT this is
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* wrong. Family 0x10 and 0x11 CPUs will enter C1 on HLT. Powersavings
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* then depend on a clock divisor and current Pstate of the core. If
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* all cores of a processor are in halt state (C1) the processor can
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* enter the C1E (C1 enhanced) state. If mwait is used this will never
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* happen.
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*
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* idle=mwait overrides this decision and forces the usage of mwait.
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*/
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#define MWAIT_INFO 0x05
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#define MWAIT_ECX_EXTENDED_INFO 0x01
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#define MWAIT_EDX_C1 0xf0
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int mwait_usable(const struct cpuinfo_x86 *c)
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{
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u32 eax, ebx, ecx, edx;
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/* Use mwait if idle=mwait boot option is given */
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if (boot_option_idle_override == IDLE_FORCE_MWAIT)
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return 1;
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/*
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* Any idle= boot option other than idle=mwait means that we must not
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* use mwait. Eg: idle=halt or idle=poll or idle=nomwait
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*/
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if (boot_option_idle_override != IDLE_NO_OVERRIDE)
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return 0;
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if (c->cpuid_level < MWAIT_INFO)
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return 0;
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cpuid(MWAIT_INFO, &eax, &ebx, &ecx, &edx);
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/* Check, whether EDX has extended info about MWAIT */
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if (!(ecx & MWAIT_ECX_EXTENDED_INFO))
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return 1;
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/*
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* edx enumeratios MONITOR/MWAIT extensions. Check, whether
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* C1 supports MWAIT
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*/
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return (edx & MWAIT_EDX_C1);
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}
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bool amd_e400_c1e_detected;
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bool amd_e400_c1e_detected;
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EXPORT_SYMBOL(amd_e400_c1e_detected);
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EXPORT_SYMBOL(amd_e400_c1e_detected);
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@ -576,13 +508,7 @@ void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
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if (pm_idle)
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if (pm_idle)
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return;
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return;
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if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
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if (cpu_has_amd_erratum(amd_erratum_400)) {
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/*
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* One CPU supports mwait => All CPUs supports mwait
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*/
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pr_info("using mwait in idle threads\n");
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pm_idle = mwait_idle;
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} else if (cpu_has_amd_erratum(amd_erratum_400)) {
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/* E400: APIC timer interrupt does not wake up CPU from C1e */
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/* E400: APIC timer interrupt does not wake up CPU from C1e */
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pr_info("using AMD E400 aware idle routine\n");
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pr_info("using AMD E400 aware idle routine\n");
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pm_idle = amd_e400_idle;
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pm_idle = amd_e400_idle;
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@ -606,9 +532,6 @@ static int __init idle_setup(char *str)
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pr_info("using polling idle threads\n");
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pr_info("using polling idle threads\n");
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pm_idle = poll_idle;
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pm_idle = poll_idle;
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boot_option_idle_override = IDLE_POLL;
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boot_option_idle_override = IDLE_POLL;
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} else if (!strcmp(str, "mwait")) {
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boot_option_idle_override = IDLE_FORCE_MWAIT;
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WARN_ONCE(1, "\"idle=mwait\" will be removed in 2012\n");
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} else if (!strcmp(str, "halt")) {
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} else if (!strcmp(str, "halt")) {
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/*
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/*
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* When the boot option of idle=halt is added, halt is
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* When the boot option of idle=halt is added, halt is
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@ -1369,7 +1369,7 @@ static inline void mwait_play_dead(void)
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void *mwait_ptr;
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void *mwait_ptr;
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struct cpuinfo_x86 *c = __this_cpu_ptr(&cpu_info);
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struct cpuinfo_x86 *c = __this_cpu_ptr(&cpu_info);
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if (!(this_cpu_has(X86_FEATURE_MWAIT) && mwait_usable(c)))
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if (!this_cpu_has(X86_FEATURE_MWAIT))
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return;
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return;
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if (!this_cpu_has(X86_FEATURE_CLFLSH))
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if (!this_cpu_has(X86_FEATURE_CLFLSH))
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return;
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return;
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@ -84,7 +84,6 @@ static DEFINE_PER_CPU(struct cpuidle_device *, acpi_cpuidle_device);
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static int disabled_by_idle_boot_param(void)
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static int disabled_by_idle_boot_param(void)
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{
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{
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return boot_option_idle_override == IDLE_POLL ||
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return boot_option_idle_override == IDLE_POLL ||
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boot_option_idle_override == IDLE_FORCE_MWAIT ||
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boot_option_idle_override == IDLE_HALT;
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boot_option_idle_override == IDLE_HALT;
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}
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}
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