Commit 7d5f9c0f authored by Zwane Mwaikambo's avatar Zwane Mwaikambo Committed by Tony Luck

[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: default avatarZwane Mwaikambo <zwane@arm.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent de7548d0
......@@ -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);
......@@ -223,19 +223,30 @@ static inline void play_dead(void)
}
#endif /* CONFIG_HOTPLUG_CPU */
void cpu_idle_wait(void)
{
int cpu;
unsigned int cpu, this_cpu = get_cpu();
cpumask_t map;
for_each_online_cpu(cpu)
cpu_set(cpu, cpu_idle_map);
set_cpus_allowed(current, cpumask_of_cpu(this_cpu));
put_cpu();
cpus_clear(map);
for_each_online_cpu(cpu) {
per_cpu(cpu_idle_state, cpu) = 1;
cpu_set(cpu, map);
}
__get_cpu_var(cpu_idle_state) = 0;
wmb();
do {
ssleep(1);
cpus_and(map, cpu_idle_map, cpu_online_map);
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;
......
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