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>

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 76561d20ea2f27f0edfd0eee6d043b98c6aa6e90..01171f6c2c3747b51e2e1df0dba4d5c843b24be1 100644 (file)
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -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,

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 5079f24c955a2d3b9b66532cd2c8cd45e5116d14..9f98eb400fefa9c238822cc3b1ea92ded788e0e1 100644 (file)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -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));
 

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 083e99d1b7df2aba236563467f47ebb21a09943d..837c81e99edf6d482320bf20a44710c784159b5e 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -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();

diff --git a/kernel/cpu.c b/kernel/cpu.c
index f6e726f184916029e2d1cfdbcd4acb2b26f14e69..8ccc182069ecfc62a3a4331449f46e971ccb40c9 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -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 */