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Subject[PATCH] NUMA-Q disable irqbalance
This patch is from Matt Dobson. It disables irq_balance for the NUMA-Q
and makes it a config option for everyone else. This is needed for NUMA-Q
to work, since the irq_balance code assumes a logical flat apic addressing
mode that's not true in all cases. We created a config option since
irq_balance makes performance significantly worse for some workloads.

Please apply,

Martin.

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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