On Tuesday, December 14, 2010, tip-bot for Suresh Siddha wrote: > Commit-ID: 3fb82d56ad003e804923185316236f26b30dfdd5 > Gitweb: http://git.kernel.org/tip/3fb82d56ad003e804923185316236f26b30dfdd5 > Author: Suresh Siddha <suresh.b.siddha@xxxxxxxxx> > AuthorDate: Tue, 23 Nov 2010 16:11:40 -0800 > Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> > CommitDate: Mon, 13 Dec 2010 16:23:56 -0800 > > 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@xxxxxxxxx> > LKML-Reference: <1290557500.4946.8.camel@xxxxxxxxxxxxxxxxxxxxxxxxxxx> > Cc: Rafael J. Wysocki <rjw@xxxxxxx> > Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> OK, I guess there's no nicer way to implement that. Acked-by: Rafael J. Wysocki <rjw@xxxxxxx> > --- > arch/x86/include/asm/alternative.h | 1 + > arch/x86/kernel/alternative.c | 3 ++- > arch/x86/kernel/smpboot.c | 14 ++++++++++++++ > kernel/cpu.c | 11 +++++++++++ > 4 files changed, 28 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h > index 76561d2..01171f6 100644 > --- 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 5079f24..9f98eb4 100644 > --- 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 083e99d..837c81e 100644 > --- 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 f6e726f..8ccc182 100644 > --- 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 */ > > -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html