--- linux-2.6/arch/x86_64/kernel/io_apic.c	2006-10-23 18:44:05.000000000 -0700
+++ linux-2.6.xx/arch/x86_64/kernel/io_apic.c	2006-10-23 18:10:08.000000000 -0700
@@ -613,8 +613,9 @@
 	 * 0x80, because int 0x80 is hm, kind of importantish. ;)
 	 */
 	static int current_vector = FIRST_DEVICE_VECTOR, current_offset = 0;
-	int old_vector = -1;
-	int cpu;
+	int vector = -1, old_vector = -1;
+	cpumask_t domain, new_mask;
+	int cpu, new_cpu;
 
 	BUG_ON((unsigned)irq >= NR_IRQ_VECTORS);
 
@@ -624,15 +625,30 @@
 	if (irq_vector[irq] > 0)
 		old_vector = irq_vector[irq];
 	if (old_vector > 0) {
-		cpus_and(*result, irq_domain[irq], mask);
-		if (!cpus_empty(*result))
-			return old_vector;
+		/* try to reuse vector */
+		for_each_cpu_mask(cpu, mask) {
+			int can_reuse = 1;
+			domain = vector_allocation_domain(cpu);
+			cpus_and(new_mask, domain, cpu_online_map);
+			for_each_cpu_mask(new_cpu, new_mask) {
+				int old_irq;
+				old_irq = per_cpu(vector_irq, new_cpu)[old_vector];
+				if ( (old_irq != irq) && (old_irq != -1)) {
+					can_reuse = 0;
+					break;
+				}
+			}
+
+			if(!can_reuse) continue;
+
+			vector = old_vector;
+			goto found_one;	
+		}
+
 	}
 
 	for_each_cpu_mask(cpu, mask) {
-		cpumask_t domain, new_mask;
-		int new_cpu;
-		int vector, offset;
+		int offset;
 
 		domain = vector_allocation_domain(cpu);
 		cpus_and(new_mask, domain, cpu_online_map);
@@ -656,21 +672,27 @@
 		/* Found one! */
 		current_vector = vector;
 		current_offset = offset;
-		if (old_vector >= 0) {
-			cpumask_t old_mask;
-			int old_cpu;
-			cpus_and(old_mask, irq_domain[irq], cpu_online_map);
-			for_each_cpu_mask(old_cpu, old_mask)
-				per_cpu(vector_irq, old_cpu)[old_vector] = -1;
-		}
-		for_each_cpu_mask(new_cpu, new_mask)
-			per_cpu(vector_irq, new_cpu)[vector] = irq;
-		irq_vector[irq] = vector;
-		irq_domain[irq] = domain;
-		cpus_and(*result, domain, mask);
-		return vector;
+		
+		goto found_one;
 	}
+
 	return -ENOSPC;
+
+found_one:
+	if (old_vector >= 0) {
+		cpumask_t old_mask;
+		int old_cpu;
+		cpus_and(old_mask, irq_domain[irq], cpu_online_map);
+		for_each_cpu_mask(old_cpu, old_mask)
+			per_cpu(vector_irq, old_cpu)[old_vector] = -1;
+	}
+	for_each_cpu_mask(new_cpu, new_mask)
+		per_cpu(vector_irq, new_cpu)[vector] = irq;
+	irq_vector[irq] = vector;
+	irq_domain[irq] = domain;
+	cpus_and(*result, domain, mask);
+	return vector;
+
 }
 
 static int assign_irq_vector(int irq, cpumask_t mask, cpumask_t *result)