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Commit 3fb82d56 authored by Suresh Siddha's avatar Suresh Siddha Committed by H. Peter Anvin
Browse files

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: default avatarSuresh 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: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent cf7d7e5a

arch/x86/include/asm/alternative.h

+1 −0
Original line number Diff line number Diff line
@@ -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,

arch/x86/kernel/alternative.c

+2 −1
Original line number Diff line number Diff line
@@ -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));

arch/x86/kernel/smpboot.c

+14 −0
Original line number Diff line number Diff line
@@ -1166,6 +1166,20 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus) 
	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();

kernel/cpu.c

+11 −0
Original line number Diff line number Diff line
@@ -386,6 +386,14 @@ int __cpuinit cpu_up(unsigned int cpu) 
#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 */