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Message-Id: <1314397924-10236-2-git-send-email-andi@firstfloor.org>
Date: Fri, 26 Aug 2011 15:32:03 -0700
From: Andi Kleen <andi@...stfloor.org>
To: tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org, tim.c.chen@...ux.intel.com,
Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 2/3] broadcast-tick: Move oneshot broadcast mask to per cpu variables
From: Andi Kleen <ak@...ux.intel.com>
Avoid a global cache line hotspot in the oneshot cpu mask. Maintain
this information in per cpu variables instead.
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
include/linux/tick.h | 2 +-
kernel/time/tick-broadcast.c | 40 ++++++++++++++++++++++++----------------
kernel/time/timer_list.c | 11 +++++++++--
3 files changed, 34 insertions(+), 19 deletions(-)
diff --git a/include/linux/tick.h b/include/linux/tick.h
index b232ccc..3df6e2e 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -90,7 +90,7 @@ extern struct tick_device *tick_get_broadcast_device(void);
extern struct cpumask *tick_get_broadcast_mask(void);
# ifdef CONFIG_TICK_ONESHOT
-extern struct cpumask *tick_get_broadcast_oneshot_mask(void);
+extern void tick_get_broadcast_oneshot_mask(struct cpumask *);
# endif
# endif /* BROADCAST */
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index c7218d1..7f33b15 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -358,15 +358,22 @@ int tick_resume_broadcast(void)
#ifdef CONFIG_TICK_ONESHOT
-/* FIXME: use cpumask_var_t. */
-static DECLARE_BITMAP(tick_broadcast_oneshot_mask, NR_CPUS);
+struct broadcast_cpu_state {
+ int need_oneshot;
+} ____cacheline_aligned;
+static DEFINE_PER_CPU(struct broadcast_cpu_state, state);
/*
* Exposed for debugging: see timer_list.c
*/
-struct cpumask *tick_get_broadcast_oneshot_mask(void)
+void tick_get_broadcast_oneshot_mask(struct cpumask *mask)
{
- return to_cpumask(tick_broadcast_oneshot_mask);
+ int i;
+
+ for_each_online_cpu (i) {
+ if (per_cpu(state, i).need_oneshot)
+ cpumask_set_cpu(i, mask);
+ }
}
static int tick_broadcast_set_event(ktime_t expires, int force)
@@ -388,7 +395,7 @@ int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
*/
void tick_check_oneshot_broadcast(int cpu)
{
- if (cpumask_test_cpu(cpu, to_cpumask(tick_broadcast_oneshot_mask))) {
+ if (per_cpu(state, cpu).need_oneshot) {
struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT);
@@ -411,7 +418,9 @@ again:
cpumask_clear(to_cpumask(tmpmask));
now = ktime_get();
/* Find all expired events */
- for_each_cpu(cpu, tick_get_broadcast_oneshot_mask()) {
+ for_each_online_cpu(cpu) {
+ if (!per_cpu(state, cpu).need_oneshot)
+ continue;
td = &per_cpu(tick_cpu_device, cpu);
if (td->evtdev->next_event.tv64 <= now.tv64)
cpumask_set_cpu(cpu, to_cpumask(tmpmask));
@@ -478,16 +487,15 @@ void tick_broadcast_oneshot_control(unsigned long reason)
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
- if (!cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
- cpumask_set_cpu(cpu, tick_get_broadcast_oneshot_mask());
+ if (!__get_cpu_var(state).need_oneshot) {
+ __get_cpu_var(state).need_oneshot = 1;
clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
if (dev->next_event.tv64 < bc->next_event.tv64)
tick_broadcast_set_event(dev->next_event, 1);
}
} else {
- if (cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
- cpumask_clear_cpu(cpu,
- tick_get_broadcast_oneshot_mask());
+ if (__get_cpu_var(state).need_oneshot) {
+ __get_cpu_var(state).need_oneshot = 0;
clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
if (dev->next_event.tv64 != KTIME_MAX)
tick_program_event(dev->next_event, 1);
@@ -503,7 +511,7 @@ void tick_broadcast_oneshot_control(unsigned long reason)
*/
static void tick_broadcast_clear_oneshot(int cpu)
{
- cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
+ per_cpu(state, cpu).need_oneshot = 0;
}
static void tick_broadcast_init_next_event(struct cpumask *mask,
@@ -529,6 +537,7 @@ void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
/* Set it up only once ! */
if (bc->event_handler != tick_handle_oneshot_broadcast) {
int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;
+ int i;
bc->event_handler = tick_handle_oneshot_broadcast;
clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
@@ -544,9 +553,8 @@ void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
*/
cpumask_copy(to_cpumask(tmpmask), tick_get_broadcast_mask());
cpumask_clear_cpu(cpu, to_cpumask(tmpmask));
- cpumask_or(tick_get_broadcast_oneshot_mask(),
- tick_get_broadcast_oneshot_mask(),
- to_cpumask(tmpmask));
+ for_each_cpu (i, to_cpumask(tmpmask))
+ per_cpu(state, i).need_oneshot = 1;
if (was_periodic && !cpumask_empty(to_cpumask(tmpmask))) {
tick_broadcast_init_next_event(to_cpumask(tmpmask),
@@ -598,7 +606,7 @@ void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
* Clear the broadcast mask flag for the dead cpu, but do not
* stop the broadcast device!
*/
- cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
+ per_cpu(state, cpu).need_oneshot = 0;
raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}
diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index 3258455..28964ed 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -235,14 +235,21 @@ print_tickdevice(struct seq_file *m, struct tick_device *td, int cpu)
static void timer_list_show_tickdevices(struct seq_file *m)
{
int cpu;
+#ifdef CONFIG_TICK_ONESHOT
+ cpumask_var_t mask;
+#endif
#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
print_tickdevice(m, tick_get_broadcast_device(), -1);
SEQ_printf(m, "tick_broadcast_mask: %08lx\n",
cpumask_bits(tick_get_broadcast_mask())[0]);
#ifdef CONFIG_TICK_ONESHOT
- SEQ_printf(m, "tick_broadcast_oneshot_mask: %08lx\n",
- cpumask_bits(tick_get_broadcast_oneshot_mask())[0]);
+ if (zalloc_cpumask_var(&mask, GFP_KERNEL) == 0) {
+ tick_get_broadcast_oneshot_mask(mask);
+ SEQ_printf(m, "tick_broadcast_oneshot_mask: %08lx\n",
+ cpumask_bits(mask)[0]);
+ free_cpumask_var(mask);
+ }
#endif
SEQ_printf(m, "\n");
#endif
--
1.7.4.4
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