[Xen-devel] [PATCH4/6] cpuidle: remove hpet access in hpet_broadcast_exit

["Wei, Gang" <gang.wei@xxxxxxxxx>]

cpuidle: remove hpet access in hpet_broadcast_exit

hpet_broadcast_exit calls reprogram_hpet to stop possible hpet intr if the last 
deep-cstate waken up cpu is waken by unexpected intrs instead of hpet broadcast 
handler. This can be removed without brings much useless intrs, but bring 
chance for further optimization. It is a tradeoff between grace & optimization.

BTW, move the cpumask set out of critial section in hpet_broadcast_enter to 
shorten it.

Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>

diff -r 451a46c667c9 xen/arch/x86/hpet.c
--- a/xen/arch/x86/hpet.c       Sun Jun 13 07:23:26 2010 +0800
+++ b/xen/arch/x86/hpet.c       Sun Jun 13 07:27:14 2010 +0800
@@ -664,14 +664,12 @@ void hpet_broadcast_enter(void)
 
     /* Disable LAPIC timer interrupts. */
     disable_APIC_timer();
+    cpu_set(cpu, ch->cpumask);
 
     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);
-
     spin_unlock(&ch->lock);
 }
 
@@ -692,11 +690,7 @@ void hpet_broadcast_exit(void)
         raise_softirq(TIMER_SOFTIRQ);
 
     spin_lock_irq(&ch->lock);
-
     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 ( ch != &legacy_hpet_event )

Attachment: 4-deepc-wakeup-optimize-1.patch
Description: 4-deepc-wakeup-optimize-1.patch

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