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authorZwane Mwaikambo <zwane@arm.linux.org.uk>2005-03-30 21:40:00 -0700
committerTony Luck <tony.luck@intel.com>2005-05-03 13:40:18 -0700
commit7d5f9c0f10255000ca007fb03773c6b825c2b9ce (patch)
tree5f53e41ef4cbe5ced2c5884ee5dde8df1fcaa509 /arch/ia64/kernel/process.c
parentde7548d0e202263bb6bfd7574a7889e85a691937 (diff)
[IA64] reduce cacheline bouncing in cpu_idle_wait
Andi noted that during normal runtime cpu_idle_map is bounced around a lot, and occassionally at a higher frequency than the timer interrupt wakeup which we normally exit pm_idle from. So switch to a percpu variable. I didn't move things to the slow path because it would involve adding scheduler code to wakeup the idle thread on the cpus we're waiting for. Signed-off-by: Zwane Mwaikambo <zwane@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Tony Luck <tony.luck@intel.com>
Diffstat (limited to 'arch/ia64/kernel/process.c')
-rw-r--r--arch/ia64/kernel/process.c41
1 files changed, 26 insertions, 15 deletions
diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index 7c43aea5f7f..c0140f4235e 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -50,7 +50,7 @@
#include "sigframe.h"
void (*ia64_mark_idle)(int);
-static cpumask_t cpu_idle_map;
+static DEFINE_PER_CPU(unsigned int, cpu_idle_state);
unsigned long boot_option_idle_override = 0;
EXPORT_SYMBOL(boot_option_idle_override);
@@ -223,20 +223,31 @@ static inline void play_dead(void)
}
#endif /* CONFIG_HOTPLUG_CPU */
-
void cpu_idle_wait(void)
{
- int cpu;
- cpumask_t map;
+ unsigned int cpu, this_cpu = get_cpu();
+ cpumask_t map;
+
+ set_cpus_allowed(current, cpumask_of_cpu(this_cpu));
+ put_cpu();
- for_each_online_cpu(cpu)
- cpu_set(cpu, cpu_idle_map);
+ cpus_clear(map);
+ for_each_online_cpu(cpu) {
+ per_cpu(cpu_idle_state, cpu) = 1;
+ cpu_set(cpu, map);
+ }
- wmb();
- do {
- ssleep(1);
- cpus_and(map, cpu_idle_map, cpu_online_map);
- } while (!cpus_empty(map));
+ __get_cpu_var(cpu_idle_state) = 0;
+
+ wmb();
+ do {
+ ssleep(1);
+ for_each_online_cpu(cpu) {
+ if (cpu_isset(cpu, map) && !per_cpu(cpu_idle_state, cpu))
+ cpu_clear(cpu, map);
+ }
+ cpus_and(map, map, cpu_online_map);
+ } while (!cpus_empty(map));
}
EXPORT_SYMBOL_GPL(cpu_idle_wait);
@@ -244,7 +255,6 @@ void __attribute__((noreturn))
cpu_idle (void)
{
void (*mark_idle)(int) = ia64_mark_idle;
- int cpu = smp_processor_id();
/* endless idle loop with no priority at all */
while (1) {
@@ -255,12 +265,13 @@ cpu_idle (void)
while (!need_resched()) {
void (*idle)(void);
+ if (__get_cpu_var(cpu_idle_state))
+ __get_cpu_var(cpu_idle_state) = 0;
+
+ rmb();
if (mark_idle)
(*mark_idle)(1);
- if (cpu_isset(cpu, cpu_idle_map))
- cpu_clear(cpu, cpu_idle_map);
- rmb();
idle = pm_idle;
if (!idle)
idle = default_idle;