# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1272973968 -3600
# Node ID 793bc267e88338093b0012c7c0b404cd61853c16
# Parent fd44f1c0d3d6530acdf682ebdabc49308d1bfbfb
CPUIDLE: shorten hpet spin_lock holding time
Try to reduce spin_lock overhead for deep C state entry/exit. This
will benefit systems with a lot of cpus which need the hpet broadcast
to wakeup from deep C state.
Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>
---
xen/arch/x86/hpet.c | 65 ++++++++++++++++++++++++++++++++++++----------------
1 files changed, 45 insertions(+), 20 deletions(-)
diff -r fd44f1c0d3d6 -r 793bc267e883 xen/arch/x86/hpet.c
--- a/xen/arch/x86/hpet.c Tue May 04 12:51:33 2010 +0100
+++ b/xen/arch/x86/hpet.c Tue May 04 12:52:48 2010 +0100
@@ -186,6 +186,9 @@ static void handle_hpet_broadcast(struct
again:
ch->next_event = STIME_MAX;
+
+ spin_unlock_irq(&ch->lock);
+
next_event = STIME_MAX;
mask = (cpumask_t)CPU_MASK_NONE;
now = NOW();
@@ -193,10 +196,17 @@ again:
/* find all expired events */
for_each_cpu_mask(cpu, ch->cpumask)
{
- if ( per_cpu(timer_deadline_start, cpu) <= now )
- cpu_set(cpu, mask);
- else if ( per_cpu(timer_deadline_end, cpu) < next_event )
- next_event = per_cpu(timer_deadline_end, cpu);
+ spin_lock_irq(&ch->lock);
+
+ if ( cpumask_test_cpu(cpu, ch->cpumask) )
+ {
+ if ( per_cpu(timer_deadline_start, cpu) <= now )
+ cpu_set(cpu, mask);
+ else if ( per_cpu(timer_deadline_end, cpu) < next_event )
+ next_event = per_cpu(timer_deadline_end, cpu);
+ }
+
+ spin_unlock_irq(&ch->lock);
}
/* wakeup the cpus which have an expired event. */
@@ -204,10 +214,14 @@ again:
if ( next_event != STIME_MAX )
{
- if ( reprogram_hpet_evt_channel(ch, next_event, now, 0) )
+ spin_lock_irq(&ch->lock);
+
+ if ( next_event < ch->next_event &&
+ reprogram_hpet_evt_channel(ch, next_event, now, 0) )
goto again;
- }
- spin_unlock_irq(&ch->lock);
+
+ spin_unlock_irq(&ch->lock);
+ }
}
static void hpet_interrupt_handler(int irq, void *data,
@@ -656,17 +670,23 @@ void hpet_broadcast_enter(void)
BUG_ON( !ch );
ASSERT(!local_irq_is_enabled());
- spin_lock(&ch->lock);
if ( hpet_attach_channel )
+ {
+ spin_lock(&ch->lock);
+
hpet_attach_channel(cpu, ch);
+
+ spin_unlock(&ch->lock);
+ }
/* Cancel any outstanding LAPIC timer event and disable interrupts. */
reprogram_timer(0);
disable_APIC_timer();
+ spin_lock(&ch->lock);
+
cpu_set(cpu, ch->cpumask);
-
/* reprogram if current cpu expire time is nearer */
if ( this_cpu(timer_deadline_end) < ch->next_event )
reprogram_hpet_evt_channel(ch, this_cpu(timer_deadline_end), NOW(), 1);
@@ -684,23 +704,28 @@ void hpet_broadcast_exit(void)
BUG_ON( !ch );
+ /* Reprogram the deadline; trigger timer work now if it has passed. */
+ enable_APIC_timer();
+ if ( !reprogram_timer(this_cpu(timer_deadline_start)) )
+ raise_softirq(TIMER_SOFTIRQ);
+
spin_lock_irq(&ch->lock);
- if ( cpu_test_and_clear(cpu, ch->cpumask) )
- {
- /* Reprogram the deadline; trigger timer work now if it has passed. */
- enable_APIC_timer();
- if ( !reprogram_timer(this_cpu(timer_deadline_start)) )
- raise_softirq(TIMER_SOFTIRQ);
-
- if ( cpus_empty(ch->cpumask) && ch->next_event != STIME_MAX )
- reprogram_hpet_evt_channel(ch, STIME_MAX, 0, 0);
- }
+ cpu_clear(cpu, ch->cpumask);
+ if ( cpus_empty(ch->cpumask) && ch->next_event != STIME_MAX )
+ reprogram_hpet_evt_channel(ch, STIME_MAX, 0, 0);
+
+ spin_unlock_irq(&ch->lock);
+
if ( hpet_detach_channel )
+ {
+ spin_lock_irq(&ch->lock);
+
hpet_detach_channel(cpu);
- spin_unlock_irq(&ch->lock);
+ spin_unlock_irq(&ch->lock);
+ }
}
int hpet_broadcast_is_available(void)
_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog
|
Home