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Date: Tue, 14 Dec 2010 21:21:57 GMT
From: tip-bot for Suresh Siddha <suresh.b.siddha@...el.com>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
suresh.b.siddha@...el.com, tglx@...utronix.de, hpa@...ux.intel.com,
rjw@...k.pl
Subject: [tip:x86/alternatives] x86, suspend: Avoid unnecessary smp alternatives switch during suspend/resume
Commit-ID: 3fb82d56ad003e804923185316236f26b30dfdd5
Gitweb: http://git.kernel.org/tip/3fb82d56ad003e804923185316236f26b30dfdd5
Author: Suresh Siddha <suresh.b.siddha@...el.com>
AuthorDate: Tue, 23 Nov 2010 16:11:40 -0800
Committer: H. Peter Anvin <hpa@...ux.intel.com>
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@...el.com>
LKML-Reference: <1290557500.4946.8.camel@...iddha-MOBL3.sc.intel.com>
Cc: Rafael J. Wysocki <rjw@...k.pl>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
---
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 */
--
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