# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
#	           ChangeSet	1.489   -> 1.490  
#	arch/i386/kernel/io_apic.c	1.26    -> 1.27   
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/08/19	haveblue@elm3b96.(none)	1.490
# Reduce irqbalance's dependence on HZ.  Only write to io_apic when there is actually
# a change to write into it.  
# --------------------------------------------
#
diff -Nru a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c
--- a/arch/i386/kernel/io_apic.c	Mon Aug 19 14:49:03 2002
+++ b/arch/i386/kernel/io_apic.c	Mon Aug 19 14:49:03 2002
@@ -220,6 +220,9 @@
 		((1 << cpu) & (allowed_mask))
 
 #if CONFIG_SMP
+
+#define IRQ_BALANCE_INTERVAL (HZ/50)
+	
 static unsigned long move(int curr_cpu, unsigned long allowed_mask, unsigned long now, int direction)
 {
 	int search_idle = 1;
@@ -254,8 +257,9 @@
 	if (clustered_apic_mode)
 		return;
 
-	if (entry->timestamp != now) {
+	if (unlikely(time_after(now, entry->timestamp + IRQ_BALANCE_INTERVAL))) {
 		unsigned long allowed_mask;
+		unsigned int new_cpu;
 		int random_number;
 
 		rdtscl(random_number);
@@ -263,8 +267,11 @@
 
 		allowed_mask = cpu_online_map & irq_affinity[irq];
 		entry->timestamp = now;
-		entry->cpu = move(entry->cpu, allowed_mask, now, random_number);
-		set_ioapic_affinity(irq, 1 << entry->cpu);
+		new_cpu = move(entry->cpu, allowed_mask, now, random_number);
+		if (entry->cpu != new_cpu) {
+			entry->cpu = new_cpu;
+			set_ioapic_affinity(irq, 1 << new_cpu);
+		}
 	}
 }
 #else /* !SMP */