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x86_64: speedup touch_nmi_watchdog 

Avoid dirtying remote cpu's memory if it already has the correct value.

Cc: Andi Kleen <ak@suse.de>
Cc: Konrad Rzeszutek <konrad@darnok.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrew Morton 2007-07-17 04:03:58 -07:00 committed by Linus Torvalds
parent f2890255b0
commit 567f3e422a
1 changed files with 5 additions and 3 deletions
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8
arch/x86_64/kernel/nmi.c
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@ -296,7 +296,7 @@ static DEFINE_PER_CPU(unsigned, last_irq_sum);
static DEFINE_PER_CPU(local_t, alert_counter); static DEFINE_PER_CPU(local_t, alert_counter);
static DEFINE_PER_CPU(int, nmi_touch); static DEFINE_PER_CPU(int, nmi_touch);
void touch_nmi_watchdog (void) void touch_nmi_watchdog(void)
{ {
if (nmi_watchdog > 0) { if (nmi_watchdog > 0) {
unsigned cpu; unsigned cpu;
@ -306,8 +306,10 @@ void touch_nmi_watchdog (void)
* do it ourselves because the alert count increase is not * do it ourselves because the alert count increase is not
* atomic. * atomic.
*/ */
for_each_present_cpu (cpu) for_each_present_cpu(cpu) {
per_cpu(nmi_touch, cpu) = 1; if (per_cpu(nmi_touch, cpu) != 1)
per_cpu(nmi_touch, cpu) = 1;
}
} }
touch_softlockup_watchdog(); touch_softlockup_watchdog();