IRQ Balancing doesn't work on some hardware platforms or systems with > 8 CPUs.
Some benchmarks have also showed that the irq_balancing code is actually a
performance hit in many cases. For these reasons, I've created a config option
to turn of IRQ Balancing if desired. Attatched is the patch...
Cheers!
-Matt
diff -Nur linux-2.5.25-vanilla/arch/i386/Config.help linux-2.5.25-patched/arch/i386/Config.help
--- linux-2.5.25-vanilla/arch/i386/Config.help Fri Jul 5 16:42:04 2002
+++ linux-2.5.25-patched/arch/i386/Config.help Thu Jul 11 17:27:01 2002
@@ -41,6 +41,12 @@
486, 586, Pentiums, and various instruction-set-compatible chips by
AMD, Cyrix, and others.
+CONFIG_IRQ_BALANCE
+ This option is used to turn IRQ Balancing on machines with multiple
+ APIC's (ie: SMP, NUMA, etc) on or off. This behavior has been seen
+ under some conditions to reduce performance, and on some platorms causes
+ interesting hangs, particularly those with more than 8 CPUs.
+
CONFIG_MULTIQUAD
This option is used for getting Linux to run on a (IBM/Sequent) NUMA
multiquad box. This changes the way that processors are bootstrapped,
diff -Nur linux-2.5.25-vanilla/arch/i386/config.in linux-2.5.25-patched/arch/i386/config.in
--- linux-2.5.25-vanilla/arch/i386/config.in Fri Jul 5 16:42:20 2002
+++ linux-2.5.25-patched/arch/i386/config.in Thu Jul 11 17:16:52 2002
@@ -164,8 +164,19 @@
if [ "$CONFIG_X86_UP_IOAPIC" = "y" ]; then
define_bool CONFIG_X86_IO_APIC y
fi
+ define_bool CONFIG_IRQBALANCE n
else
bool 'Multiquad NUMA system' CONFIG_MULTIQUAD
+ if [ "$CONFIG_MULTIQUAD" = "y" ]; then
+ define_bool CONFIG_IRQBALANCE_DISABLE y
+ else
+ bool 'Turn Off IRQ Balancing' CONFIG_IRQBALANCE_DISABLE
+ fi
+ if [ "$CONFIG_IRQBALANCE_DISABLE" = "y" ]; then
+ define_bool CONFIG_IRQBALANCE n
+ else
+ define_bool CONFIG_IRQBALANCE y
+ fi
fi
bool 'Machine Check Exception' CONFIG_X86_MCE
diff -Nur linux-2.5.25-vanilla/arch/i386/kernel/io_apic.c linux-2.5.25-patched/arch/i386/kernel/io_apic.c
--- linux-2.5.25-vanilla/arch/i386/kernel/io_apic.c Fri Jul 5 16:42:20 2002
+++ linux-2.5.25-patched/arch/i386/kernel/io_apic.c Thu Jul 11 16:12:28 2002
@@ -199,7 +199,7 @@
spin_unlock_irqrestore(&ioapic_lock, flags);
}
-#if CONFIG_SMP
+#if CONFIG_IRQBALANCE
typedef struct {
unsigned int cpu;
@@ -211,15 +211,12 @@
extern unsigned long irq_affinity [NR_IRQS];
-#endif
-
#define IDLE_ENOUGH(cpu,now) \
(idle_cpu(cpu) && ((now) - irq_stat[(cpu)].idle_timestamp > 1))
#define IRQ_ALLOWED(cpu,allowed_mask) \
((1 << cpu) & (allowed_mask))
-#if CONFIG_SMP
static unsigned long move(int curr_cpu, unsigned long allowed_mask, unsigned long now, int direction)
{
int search_idle = 1;
@@ -264,9 +261,9 @@
set_ioapic_affinity(irq, 1 << entry->cpu);
}
}
-#else /* !SMP */
+#else /* !CONFIG_IRQBALANCE */
static inline void balance_irq(int irq) { }
-#endif
+#endif /* CONFIG_IRQBALANCE */
/*
* support for broken MP BIOSs, enables hand-redirection of PIRQ0-7 to
-
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This archive was generated by hypermail 2b29 : Tue Jul 23 2002 - 22:00:44 EST