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x86, suspend: Avoid unnecessary smp alternatives switch during suspend/resume 

During suspend, we disable all the non boot cpus. And during resume we bring
them all back again. So no need to do alternatives_smp_switch() in between.

On my core 2 based laptop, this speeds up the suspend path by 15msec and the
resume path by 5 msec (suspend/resume speed up differences can be attributed
to the different P-states that the cpu is in during suspend/resume).

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1290557500.4946.8.camel@sbsiddha-MOBL3.sc.intel.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Suresh Siddha 2010-11-23 16:11:40 -08:00 committed by H. Peter Anvin
parent cf7d7e5a19
commit 3fb82d56ad
4 changed files with 28 additions and 1 deletions
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1
arch/x86/include/asm/alternative.h
View File

@ -66,6 +66,7 @@ extern void alternatives_smp_module_add(struct module *mod, char *name,
extern void alternatives_smp_module_del(struct module *mod);
extern void alternatives_smp_switch(int smp);
extern int alternatives_text_reserved(void *start, void *end);
extern bool skip_smp_alternatives;
#else
static inline void alternatives_smp_module_add(struct module *mod, char *name,
void *locks, void *locks_end,

3
arch/x86/kernel/alternative.c
View File

@ -353,6 +353,7 @@ void __init_or_module alternatives_smp_module_del(struct module *mod)
mutex_unlock(&smp_alt);
}
bool skip_smp_alternatives;
void alternatives_smp_switch(int smp)
{
struct smp_alt_module *mod;
@ -368,7 +369,7 @@ void alternatives_smp_switch(int smp)
printk("lockdep: fixing up alternatives.\n");
#endif
if (noreplace_smp || smp_alt_once)
if (noreplace_smp || smp_alt_once || skip_smp_alternatives)
return;
BUG_ON(!smp && (num_online_cpus() > 1));

14
arch/x86/kernel/smpboot.c
View File

@ -1166,6 +1166,20 @@ out:
preempt_enable();
}
void arch_disable_nonboot_cpus_begin(void)
{
/*
* Avoid the smp alternatives switch during the disable_nonboot_cpus().
* In the suspend path, we will be back in the SMP mode shortly anyways.
*/
skip_smp_alternatives = true;
}
void arch_disable_nonboot_cpus_end(void)
{
skip_smp_alternatives = false;
}
void arch_enable_nonboot_cpus_begin(void)
{
set_mtrr_aps_delayed_init();

11
kernel/cpu.c
View File

@ -386,6 +386,14 @@ out:
#ifdef CONFIG_PM_SLEEP_SMP
static cpumask_var_t frozen_cpus;
void __weak arch_disable_nonboot_cpus_begin(void)
{
}
void __weak arch_disable_nonboot_cpus_end(void)
{
}
int disable_nonboot_cpus(void)
{
int cpu, first_cpu, error = 0;
@ -397,6 +405,7 @@ int disable_nonboot_cpus(void)
* with the userspace trying to use the CPU hotplug at the same time
*/
cpumask_clear(frozen_cpus);
arch_disable_nonboot_cpus_begin();
printk("Disabling non-boot CPUs ...\n");
for_each_online_cpu(cpu) {
@ -412,6 +421,8 @@ int disable_nonboot_cpus(void)
}
}
arch_disable_nonboot_cpus_end();
if (!error) {
BUG_ON(num_online_cpus() > 1);
/* Make sure the CPUs won't be enabled by someone else */