The patch titled
x86: kernel irq balance doesn't work
has been added to the -mm tree. Its filename is
x86-kernel-irq-balancer-fix.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
From: Zhang Yanmin <yanmin.zhang@xxxxxxxxx>
On i386, kernel irq balance doesn't work.
1) In function do_irq_balance, after kernel finds the min_loaded cpu but
before calling set_pending_irq to really pin the selected_irq to the
target cpu, kernel does a cpus_and with irq_affinity[selected_irq].
Later on, when the irq is acked, kernel would calls
move_native_irq=>desc->handler->set_affinity to change the irq affinity.
However, every function pointed by
hw_interrupt_type->set_affinity(unsigned int irq, cpumask_t cpumask)
always changes irq_affinity[irq] to cpumask. Next time when recalling
do_irq_balance, it has to do cpu_ands again with
irq_affinity[selected_irq], but irq_affinity[selected_irq] already
becomes one cpu selected by the first irq balance.
2) Function balance_irq in file arch/i386/kernel/io_apic.c has the same
issue.
Signed-off-by: Zhang Yanmin <yanmin.zhang@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
arch/i386/kernel/io_apic.c | 15 +++++++++++++--
include/linux/irq.h | 6 ++++++
kernel/irq/proc.c | 3 +++
3 files changed, 22 insertions(+), 2 deletions(-)
diff -puN arch/i386/kernel/io_apic.c~x86-kernel-irq-balancer-fix arch/i386/kernel/io_apic.c
--- devel/arch/i386/kernel/io_apic.c~x86-kernel-irq-balancer-fix 2006-05-18 00:29:04.000000000 -0700
+++ devel-akpm/arch/i386/kernel/io_apic.c 2006-05-18 00:33:57.000000000 -0700
@@ -307,6 +307,15 @@ static struct irq_cpu_info {
static long balanced_irq_interval = MAX_BALANCED_IRQ_INTERVAL;
+static cpumask_t balance_irq_affinity[NR_IRQS] = {
+ [0 ... NR_IRQS-1] = CPU_MASK_ALL
+};
+
+void set_balance_irq_affinity(unsigned int irq, cpumask_t mask)
+{
+ balance_irq_affinity[irq] = mask;
+}
+
static unsigned long move(int curr_cpu, cpumask_t allowed_mask,
unsigned long now, int direction)
{
@@ -343,7 +352,7 @@ static inline void balance_irq(int cpu,
if (irqbalance_disabled)
return;
- cpus_and(allowed_mask, cpu_online_map, irq_affinity[irq]);
+ cpus_and(allowed_mask, cpu_online_map, balance_irq_affinity[irq]);
new_cpu = move(cpu, allowed_mask, now, 1);
if (cpu != new_cpu) {
set_pending_irq(irq, cpumask_of_cpu(new_cpu));
@@ -532,7 +541,9 @@ tryanotherirq:
}
}
- cpus_and(allowed_mask, cpu_online_map, irq_affinity[selected_irq]);
+ cpus_and(allowed_mask,
+ cpu_online_map,
+ balance_irq_affinity[selected_irq]);
target_cpu_mask = cpumask_of_cpu(min_loaded);
cpus_and(tmp, target_cpu_mask, allowed_mask);
diff -puN include/linux/irq.h~x86-kernel-irq-balancer-fix include/linux/irq.h
--- devel/include/linux/irq.h~x86-kernel-irq-balancer-fix 2006-05-18 00:29:04.000000000 -0700
+++ devel-akpm/include/linux/irq.h 2006-05-18 00:33:57.000000000 -0700
@@ -164,6 +164,12 @@ static inline void set_irq_info(int irq,
#endif // CONFIG_SMP
+#ifdef CONFIG_IRQBALANCE
+extern void set_balance_irq_affinity(unsigned int irq, cpumask_t mask);
+#else
+#define set_balance_irq_affinity(irq, mask)
+#endif
+
extern int no_irq_affinity;
extern int noirqdebug_setup(char *str);
diff -puN kernel/irq/proc.c~x86-kernel-irq-balancer-fix kernel/irq/proc.c
--- devel/kernel/irq/proc.c~x86-kernel-irq-balancer-fix 2006-05-18 00:29:04.000000000 -0700
+++ devel-akpm/kernel/irq/proc.c 2006-05-18 00:29:04.000000000 -0700
@@ -24,6 +24,8 @@ static struct proc_dir_entry *smp_affini
#ifdef CONFIG_GENERIC_PENDING_IRQ
void proc_set_irq_affinity(unsigned int irq, cpumask_t mask_val)
{
+ set_balance_irq_affinity(irq, mask_val);
+
/*
* Save these away for later use. Re-progam when the
* interrupt is pending
@@ -33,6 +35,7 @@ void proc_set_irq_affinity(unsigned int
#else
void proc_set_irq_affinity(unsigned int irq, cpumask_t mask_val)
{
+ set_balance_irq_affinity(irq, mask_val);
irq_affinity[irq] = mask_val;
irq_desc[irq].handler->set_affinity(irq, mask_val);
}
_
Patches currently in -mm which might be from yanmin.zhang@xxxxxxxxx are
x86-kernel-irq-balancer-fix.patch
x86-kernel-irq-balancer-fix-tidy.patch
-
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