[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] RE: [PATCH] CPUIDLE: shorten hpet spin_lock holding time
Resend. 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> diff -r dbf0fd95180f xen/arch/x86/hpet.c --- a/xen/arch/x86/hpet.c Tue Apr 20 14:32:53 2010 +0100 +++ b/xen/arch/x86/hpet.c Tue Apr 20 23:48:19 2010 +0800 @@ -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) Attachment:
hpet_short_lock_v2.patch _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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