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[PATCH] x86: Don't use MWAIT on AMD Family 10

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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>
This commit is contained in:
Andi Kleen 2007-05-02 19:27:12 +02:00 committed by Andi Kleen
parent c169859d6d
commit f039b75471
7 changed files with 39 additions and 16 deletions
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11
Documentation/kernel-parameters.txt
View File

@ -695,8 +695,15 @@ and is between 256 and 4096 characters. It is defined in the file
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/

5
arch/i386/kernel/cpu/amd.c
View File

@ -53,6 +53,8 @@ static __cpuinit int amd_apic_timer_broken(void)
return 0;
}
int force_mwait __cpuinitdata;
static void __cpuinit init_amd(struct cpuinfo_x86 *c)
{
u32 l, h;
@ -275,6 +277,9 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
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)

17
arch/i386/kernel/process.c
View File

@ -272,25 +272,24 @@ void __devinit select_idle_routine(const struct cpuinfo_x86 *c)
}
}
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)
{

12
arch/x86_64/kernel/process.c
View File

@ -288,16 +288,18 @@ void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
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)

6
arch/x86_64/kernel/setup.c
View File

@ -79,6 +79,8 @@ int bootloader_type;
unsigned long saved_video_mode;
int force_mwait __cpuinitdata;
/*
* Early DMI memory
*/
@ -604,6 +606,10 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
/* 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)

2
include/asm-i386/processor.h
View File

@ -779,4 +779,6 @@ extern int sysenter_setup(void);
extern void cpu_set_gdt(int);
extern void cpu_init(void);
extern int force_mwait;
#endif /* __ASM_I386_PROCESSOR_H */

2
include/asm-x86_64/proto.h
View File

@ -119,6 +119,8 @@ extern int gsi_irq_sharing(int gsi);
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);