From 69fb3676df3329a7142803bb3502fa59dc0db2e3 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Sun, 10 Feb 2013 01:38:39 -0500 Subject: 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 But mwait_idle() has been replaced by the more general mwait_idle_with_hints(), which handles both C1 and deeper C-states.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 Cc: x86@kernel.org --- Documentation/kernel-parameters.txt | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) (limited to 'Documentation') diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 363e348..3b0cd1e 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1039,16 +1039,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Claim all unknown PCI IDE storage controllers. idle= [X86] - Format: idle=poll, idle=mwait, idle=halt, idle=nomwait + Format: idle=poll, idle=halt, idle=nomwait Poll forces a polling idle loop that can slightly improve the performance of waking up a idle CPU, but will use a lot of power and make the system run hot. Not recommended. - idle=mwait: On systems which support MONITOR/MWAIT but - the kernel chose to not use it because it doesn't save - as much power as a normal idle loop, use the - MONITOR/MWAIT idle loop anyways. Performance should be - the same 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 -- cgit v1.1 From 27be457000211a6903968dfce06d5f73f051a217 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Sun, 10 Feb 2013 02:28:46 -0500 Subject: x86 idle: remove 32-bit-only "no-hlt" parameter, hlt_works_ok flag Remove 32-bit x86 a cmdline param "no-hlt", and the cpuinfo_x86.hlt_works_ok that it sets. If a user wants to avoid HLT, then "idle=poll" is much more useful, as it avoids invocation of HLT in idle, while "no-hlt" failed to do so. Indeed, hlt_works_ok was consulted in only 3 places. First, in /proc/cpuinfo where "hlt_bug yes" would be printed if and only if the user booted the system with "no-hlt" -- as there was no other code to set that flag. Second, check_hlt() would not invoke halt() if "no-hlt" were on the cmdline. Third, it was consulted in stop_this_cpu(), which is invoked by native_machine_halt()/reboot_interrupt()/smp_stop_nmi_callback() -- all cases where the machine is being shutdown/reset. The flag was not consulted in the more frequently invoked play_dead()/hlt_play_dead() used in processor offline and suspend. Since Linux-3.0 there has been a run-time notice upon "no-hlt" invocations indicating that it would be removed in 2012. Signed-off-by: Len Brown Cc: x86@kernel.org --- Documentation/kernel-parameters.txt | 4 ---- 1 file changed, 4 deletions(-) (limited to 'Documentation') diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 3b0cd1e..109ee45 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1881,10 +1881,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted. wfi(ARM) instruction doesn't work correctly and not to use it. This is also useful when using JTAG debugger. - no-hlt [BUGS=X86-32] Tells the kernel that the hlt - instruction doesn't work correctly and not to - use it. - no_file_caps Tells the kernel not to honor file capabilities. The only way then for a file to be executed with privilege is to be setuid root or executed by root. -- cgit v1.1