[PATCH] x86_64: resize NR_IRQS for large machines

[Alan Mayer]

Subject: [PATCH] x86_64: resize NR_IRQS for large machines

From: Alan Mayer <ajm@xxxxxxx>

On machines with very large numbers of cpus, tables that are dimensioned
by NR_IRQS get very large, especially the irq_desc table.  They are also
very sparsely used.  When the cpu count is > MAX_IO_APICS, use MAX_IO_APICS
to set NR_IRQS, otherwise use NR_CPUS.

Signed-off-by: Alan Mayer <ajm@xxxxxxx>

Reviewed-by: Christoph Lameter <clameter@xxxxxxx>

---

Index: v2.6.25-rc6/include/asm-x86/irq_64.h
===================================================================
--- v2.6.25-rc6.orig/include/asm-x86/irq_64.h	2008-03-19 16:52:52.000000000 -0500
+++ v2.6.25-rc6/include/asm-x86/irq_64.h	2008-03-20 16:46:51.000000000 -0500
@@ -10,6 +10,10 @@
  *	<tomsoft@xxxxxxxxxxxxxxxxxxxxxxxxx>
  */
 
+#if !defined(MAX_IO_APICS)
+#include <asm/apicdef.h>
+#endif
+
 #define TIMER_IRQ 0
 
 /*
@@ -31,7 +35,11 @@
 
 #define FIRST_SYSTEM_VECTOR	0xef   /* duplicated in hw_irq.h */
 
-#define NR_IRQS (NR_VECTORS + (32 *NR_CPUS))
+#if NR_CPUS < MAX_IO_APICS
+#define NR_IRQS (NR_VECTORS + (32 * NR_CPUS))
+#else
+#define NR_IRQS (NR_VECTORS + (32 * MAX_IO_APICS))
+#endif
 #define NR_IRQ_VECTORS NR_IRQS
 
 static __inline__ int irq_canonicalize(int irq)
Index: v2.6.25-rc6/include/linux/kernel_stat.h
===================================================================
--- v2.6.25-rc6.orig/include/linux/kernel_stat.h	2008-03-19 16:53:00.000000000 -0500
+++ v2.6.25-rc6/include/linux/kernel_stat.h	2008-03-20 11:12:27.000000000 -0500
@@ -1,11 +1,11 @@
 #ifndef _LINUX_KERNEL_STAT_H
 #define _LINUX_KERNEL_STAT_H
 
-#include <asm/irq.h>
 #include <linux/smp.h>
 #include <linux/threads.h>
 #include <linux/percpu.h>
 #include <linux/cpumask.h>
+#include <asm/irq.h>
 #include <asm/cputime.h>
 
 /*

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