[PATCH] reduce NMI watchdog call frequency with local APIC.

From: Mikael Pettersson <mikpe@csd.uu.se>

The real problem is that SMP with nmi_watchdog=2 initialises the lapic NMI
watchdog but doesn't check it and therefore doesn't reduce nmi_hz.  This is
an SMP bug.

The patch changes smpboot.c to do a check_nmi_watchdog() at the appropriate
place, which fixes the high NMI frequency problem w/o changing anything
else.  I've verified that it solves the problem on my MP-capable UP box.

arch/i386/kernel/smpboot.c

@@ -1114,6 +1114,9 @@ static void __init smp_boot_cpus(unsigned int max_cpus)
 			printk(KERN_WARNING "WARNING: %d siblings found for CPU%d, should be %d\n", siblings, cpu, smp_num_siblings);
 	}
 
+	if (nmi_watchdog == NMI_LOCAL_APIC)
+		check_nmi_watchdog();
+
 	smpboot_setup_io_apic();
 
 	setup_boot_APIC_clock();