[PATCH] x86: kernel irq balance doesn't work
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. [akpm@osdl.org: cleanups] Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -267,7 +267,7 @@ static void set_ioapic_affinity_irq(unsigned int irq, cpumask_t cpumask)
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# include <linux/slab.h> /* kmalloc() */
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# include <linux/timer.h> /* time_after() */
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# ifdef CONFIG_BALANCED_IRQ_DEBUG
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#ifdef CONFIG_BALANCED_IRQ_DEBUG
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# define TDprintk(x...) do { printk("<%ld:%s:%d>: ", jiffies, __FILE__, __LINE__); printk(x); } while (0)
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# define Dprintk(x...) do { TDprintk(x); } while (0)
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# else
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@ -275,10 +275,15 @@ static void set_ioapic_affinity_irq(unsigned int irq, cpumask_t cpumask)
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# define Dprintk(x...)
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# endif
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#define IRQBALANCE_CHECK_ARCH -999
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static int irqbalance_disabled = IRQBALANCE_CHECK_ARCH;
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static int physical_balance = 0;
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#define MAX_BALANCED_IRQ_INTERVAL (5*HZ)
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#define MIN_BALANCED_IRQ_INTERVAL (HZ/2)
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#define BALANCED_IRQ_MORE_DELTA (HZ/10)
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#define BALANCED_IRQ_LESS_DELTA (HZ)
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static int irqbalance_disabled __read_mostly = IRQBALANCE_CHECK_ARCH;
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static int physical_balance __read_mostly;
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static long balanced_irq_interval __read_mostly = MAX_BALANCED_IRQ_INTERVAL;
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static struct irq_cpu_info {
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unsigned long * last_irq;
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@ -297,12 +302,14 @@ static struct irq_cpu_info {
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#define CPU_TO_PACKAGEINDEX(i) (first_cpu(cpu_sibling_map[i]))
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#define MAX_BALANCED_IRQ_INTERVAL (5*HZ)
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#define MIN_BALANCED_IRQ_INTERVAL (HZ/2)
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#define BALANCED_IRQ_MORE_DELTA (HZ/10)
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#define BALANCED_IRQ_LESS_DELTA (HZ)
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static cpumask_t balance_irq_affinity[NR_IRQS] = {
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[0 ... NR_IRQS-1] = CPU_MASK_ALL
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};
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static long balanced_irq_interval = MAX_BALANCED_IRQ_INTERVAL;
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void set_balance_irq_affinity(unsigned int irq, cpumask_t mask)
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{
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balance_irq_affinity[irq] = mask;
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}
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static unsigned long move(int curr_cpu, cpumask_t allowed_mask,
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unsigned long now, int direction)
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@ -340,7 +347,7 @@ static inline void balance_irq(int cpu, int irq)
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if (irqbalance_disabled)
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return;
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cpus_and(allowed_mask, cpu_online_map, irq_affinity[irq]);
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cpus_and(allowed_mask, cpu_online_map, balance_irq_affinity[irq]);
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new_cpu = move(cpu, allowed_mask, now, 1);
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if (cpu != new_cpu) {
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set_pending_irq(irq, cpumask_of_cpu(new_cpu));
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@ -529,7 +536,9 @@ tryanotherirq:
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}
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}
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cpus_and(allowed_mask, cpu_online_map, irq_affinity[selected_irq]);
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cpus_and(allowed_mask,
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cpu_online_map,
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balance_irq_affinity[selected_irq]);
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target_cpu_mask = cpumask_of_cpu(min_loaded);
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cpus_and(tmp, target_cpu_mask, allowed_mask);
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@ -164,6 +164,14 @@ static inline void set_irq_info(int irq, cpumask_t mask)
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#endif // CONFIG_SMP
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#ifdef CONFIG_IRQBALANCE
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extern void set_balance_irq_affinity(unsigned int irq, cpumask_t mask);
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#else
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static inline void set_balance_irq_affinity(unsigned int irq, cpumask_t mask)
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{
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}
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#endif
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extern int no_irq_affinity;
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extern int noirqdebug_setup(char *str);
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@ -24,6 +24,8 @@ static struct proc_dir_entry *smp_affinity_entry[NR_IRQS];
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#ifdef CONFIG_GENERIC_PENDING_IRQ
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void proc_set_irq_affinity(unsigned int irq, cpumask_t mask_val)
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{
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set_balance_irq_affinity(irq, mask_val);
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/*
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* Save these away for later use. Re-progam when the
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* interrupt is pending
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@ -33,6 +35,7 @@ void proc_set_irq_affinity(unsigned int irq, cpumask_t mask_val)
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#else
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void proc_set_irq_affinity(unsigned int irq, cpumask_t mask_val)
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{
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set_balance_irq_affinity(irq, mask_val);
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irq_affinity[irq] = mask_val;
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irq_desc[irq].handler->set_affinity(irq, mask_val);
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}
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