[PATCH] x86: Don't use MWAIT on AMD Family 10
It doesn't put the CPU into deeper sleep states, so it's better to use the standard
idle loop to save power. But allow to reenable it anyways for benchmarking.
I also removed the obsolete idle=halt on i386
Cc: andreas.herrmann@amd.com
Signed-off-by: Andi Kleen <ak@suse.de>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4287696..94ce0d2 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -695,8 +695,15 @@
idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
See Documentation/ide.txt.
- idle= [HW]
- Format: idle=poll or idle=halt
+ idle= [X86]
+ Format: idle=poll or idle=mwait
+ 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.
+ 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.
ignore_loglevel [KNL]
Ignore loglevel setting - this will print /all/
diff --git a/arch/i386/kernel/cpu/amd.c b/arch/i386/kernel/cpu/amd.c
index 2d47db4..197cda6 100644
--- a/arch/i386/kernel/cpu/amd.c
+++ b/arch/i386/kernel/cpu/amd.c
@@ -53,6 +53,8 @@
return 0;
}
+int force_mwait __cpuinitdata;
+
static void __cpuinit init_amd(struct cpuinfo_x86 *c)
{
u32 l, h;
@@ -275,6 +277,9 @@
if (amd_apic_timer_broken())
set_bit(X86_FEATURE_LAPIC_TIMER_BROKEN, c->x86_capability);
+
+ if (c->x86 == 0x10 && !force_mwait)
+ clear_bit(X86_FEATURE_MWAIT, c->x86_capability);
}
static unsigned int __cpuinit amd_size_cache(struct cpuinfo_x86 * c, unsigned int size)
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index 393a67d..7e8e129 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -272,25 +272,24 @@
}
}
-static int __init idle_setup (char *str)
+static int __init idle_setup(char *str)
{
- if (!strncmp(str, "poll", 4)) {
+ if (!strcmp(str, "poll")) {
printk("using polling idle threads.\n");
pm_idle = poll_idle;
#ifdef CONFIG_X86_SMP
if (smp_num_siblings > 1)
printk("WARNING: polling idle and HT enabled, performance may degrade.\n");
#endif
- } else if (!strncmp(str, "halt", 4)) {
- printk("using halt in idle threads.\n");
- pm_idle = default_idle;
- }
+ } else if (!strcmp(str, "mwait"))
+ force_mwait = 1;
+ else
+ return -1;
boot_option_idle_override = 1;
- return 1;
+ return 0;
}
-
-__setup("idle=", idle_setup);
+early_param("idle", idle_setup);
void show_regs(struct pt_regs * regs)
{
diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c
index d8d5ccc..4f21765 100644
--- a/arch/x86_64/kernel/process.c
+++ b/arch/x86_64/kernel/process.c
@@ -288,16 +288,18 @@
static int __init idle_setup (char *str)
{
- if (!strncmp(str, "poll", 4)) {
+ if (!strcmp(str, "poll")) {
printk("using polling idle threads.\n");
pm_idle = poll_idle;
- }
+ } else if (!strcmp(str, "mwait"))
+ force_mwait = 1;
+ else
+ return -1;
boot_option_idle_override = 1;
- return 1;
+ return 0;
}
-
-__setup("idle=", idle_setup);
+early_param("idle", idle_setup);
/* Prints also some state that isn't saved in the pt_regs */
void __show_regs(struct pt_regs * regs)
diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index 0a1d539..db30b5b 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -79,6 +79,8 @@
unsigned long saved_video_mode;
+int force_mwait __cpuinitdata;
+
/*
* Early DMI memory
*/
@@ -604,6 +606,10 @@
/* RDTSC can be speculated around */
clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
+
+ /* Family 10 doesn't support C states in MWAIT so don't use it */
+ if (c->x86 == 0x10 && !force_mwait)
+ clear_bit(X86_FEATURE_MWAIT, &c->x86_capability);
}
static void __cpuinit detect_ht(struct cpuinfo_x86 *c)
diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index 9d895cc..882d3f8 100644
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -779,4 +779,6 @@
extern void cpu_set_gdt(int);
extern void cpu_init(void);
+extern int force_mwait;
+
#endif /* __ASM_I386_PROCESSOR_H */
diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h
index 3f8f285..98063bcb 100644
--- a/include/asm-x86_64/proto.h
+++ b/include/asm-x86_64/proto.h
@@ -119,6 +119,8 @@
extern void smp_local_timer_interrupt(void);
+extern int force_mwait;
+
long do_arch_prctl(struct task_struct *task, int code, unsigned long addr);
void i8254_timer_resume(void);