commit: 93789b32dbf355e70f18b17a82e8661677a7f7fb From: Borislav Petkov <[email protected]> Date: Thu, 20 Jan 2011 15:42:52 +0100 Subject: [PATCH] x86, hotplug: Fix powersavings with offlined cores on AMD
ea53069231f9317062910d6e772cca4ce93de8c8 made a CPU use monitor/mwait when offline. This is not the optimal choice for AMD wrt to powersavings and we'd prefer our cores to halt (i.e. enter C1) instead. For this, the same selection whether to use monitor/mwait has to be used as when we select the idle routine for the machine. With this patch, offlining cores 1-5 on a X6 machine allows core0 to boost again. [ hpa: putting this in urgent since it is a (power) regression fix ] Reported-by: Andreas Herrmann <[email protected]> Cc: [email protected] # 37.x Cc: H. Peter Anvin <[email protected]> Cc: Arjan van de Ven <[email protected]> Cc: Len Brown <[email protected]> Cc: Venkatesh Pallipadi <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> LKML-Reference: <[email protected]> Signed-off-by: H. Peter Anvin <[email protected]> --- arch/x86/include/asm/cpu.h | 1 + arch/x86/kernel/process.c | 3 ++- arch/x86/kernel/smpboot.c | 3 ++- 3 files changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index 4fab24d..6e6e755 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -32,5 +32,6 @@ extern void arch_unregister_cpu(int); DECLARE_PER_CPU(int, cpu_state); +int __cpuinit mwait_usable(const struct cpuinfo_x86 *); #endif /* _ASM_X86_CPU_H */ diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index d8286ed..e764fc0 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -14,6 +14,7 @@ #include <linux/utsname.h> #include <trace/events/power.h> #include <linux/hw_breakpoint.h> +#include <asm/cpu.h> #include <asm/system.h> #include <asm/apic.h> #include <asm/syscalls.h> @@ -505,7 +506,7 @@ static void poll_idle(void) #define MWAIT_ECX_EXTENDED_INFO 0x01 #define MWAIT_EDX_C1 0xf0 -static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c) +int __cpuinit mwait_usable(const struct cpuinfo_x86 *c) { u32 eax, ebx, ecx, edx; diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 763df77..0cbe8c0 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1402,8 +1402,9 @@ static inline void mwait_play_dead(void) unsigned int highest_subcstate = 0; int i; void *mwait_ptr; + struct cpuinfo_x86 *c = __this_cpu_ptr(&cpu_info); - if (!cpu_has(__this_cpu_ptr(&cpu_info), X86_FEATURE_MWAIT)) + if (!(cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c))) return; if (!cpu_has(__this_cpu_ptr(&cpu_info), X86_FEATURE_CLFLSH)) return; _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
