irq: use per_cpu kstat_irqs

Use modern per_cpu API to increment {soft|hard}irq counters, and use
per_cpu allocation for (struct irq_desc)->kstats_irq instead of an array.

This gives better SMP/NUMA locality and saves few instructions per irq.

With small nr_cpuids values (8 for example), kstats_irq was a small array
(less than L1_CACHE_BYTES), potentially source of false sharing.

In the !CONFIG_SPARSE_IRQ case, remove the huge, NUMA/cache unfriendly
kstat_irqs_all[NR_IRQS][NR_CPUS] array.

Note: we still populate kstats_irq for all possible irqs in
early_irq_init().  We probably could use on-demand allocations.  (Code
included in alloc_descs()).  Problem is not all IRQS are used with a prior
alloc_descs() call.

kstat_irqs_this_cpu() is not used anymore, remove it.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric Dumazet 2011-01-13 15:45:38 -08:00 committed by Linus Torvalds
parent 558bbb2fc7
commit 6c9ae009b2
3 changed files with 40 additions and 21 deletions

View File

@ -57,7 +57,7 @@ struct irq_desc {
#endif
struct timer_rand_state *timer_rand_state;
unsigned int *kstat_irqs;
unsigned int __percpu *kstat_irqs;
irq_flow_handler_t handle_irq;
struct irqaction *action; /* IRQ action list */
unsigned int status; /* IRQ status */

View File

@ -46,16 +46,14 @@ DECLARE_PER_CPU(struct kernel_stat, kstat);
extern unsigned long long nr_context_switches(void);
#ifndef CONFIG_GENERIC_HARDIRQS
#define kstat_irqs_this_cpu(irq) \
(this_cpu_read(kstat.irqs[irq])
struct irq_desc;
static inline void kstat_incr_irqs_this_cpu(unsigned int irq,
struct irq_desc *desc)
{
kstat_this_cpu.irqs[irq]++;
kstat_this_cpu.irqs_sum++;
__this_cpu_inc(kstat.irqs[irq]);
__this_cpu_inc(kstat.irqs_sum);
}
static inline unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
@ -65,17 +63,18 @@ static inline unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
#else
#include <linux/irq.h>
extern unsigned int kstat_irqs_cpu(unsigned int irq, int cpu);
#define kstat_irqs_this_cpu(DESC) \
((DESC)->kstat_irqs[smp_processor_id()])
#define kstat_incr_irqs_this_cpu(irqno, DESC) do {\
((DESC)->kstat_irqs[smp_processor_id()]++);\
kstat_this_cpu.irqs_sum++; } while (0)
#define kstat_incr_irqs_this_cpu(irqno, DESC) \
do { \
__this_cpu_inc(*(DESC)->kstat_irqs); \
__this_cpu_inc(kstat.irqs_sum); \
} while (0)
#endif
static inline void kstat_incr_softirqs_this_cpu(unsigned int irq)
{
kstat_this_cpu.softirqs[irq]++;
__this_cpu_inc(kstat.softirqs[irq]);
}
static inline unsigned int kstat_softirqs_cpu(unsigned int irq, int cpu)

View File

@ -72,6 +72,8 @@ static inline int desc_node(struct irq_desc *desc) { return 0; }
static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node)
{
int cpu;
desc->irq_data.irq = irq;
desc->irq_data.chip = &no_irq_chip;
desc->irq_data.chip_data = NULL;
@ -83,7 +85,8 @@ static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node)
desc->irq_count = 0;
desc->irqs_unhandled = 0;
desc->name = NULL;
memset(desc->kstat_irqs, 0, nr_cpu_ids * sizeof(*(desc->kstat_irqs)));
for_each_possible_cpu(cpu)
*per_cpu_ptr(desc->kstat_irqs, cpu) = 0;
desc_smp_init(desc, node);
}
@ -133,8 +136,7 @@ static struct irq_desc *alloc_desc(int irq, int node)
if (!desc)
return NULL;
/* allocate based on nr_cpu_ids */
desc->kstat_irqs = kzalloc_node(nr_cpu_ids * sizeof(*desc->kstat_irqs),
gfp, node);
desc->kstat_irqs = alloc_percpu(unsigned int);
if (!desc->kstat_irqs)
goto err_desc;
@ -149,7 +151,7 @@ static struct irq_desc *alloc_desc(int irq, int node)
return desc;
err_kstat:
kfree(desc->kstat_irqs);
free_percpu(desc->kstat_irqs);
err_desc:
kfree(desc);
return NULL;
@ -166,7 +168,7 @@ static void free_desc(unsigned int irq)
mutex_unlock(&sparse_irq_lock);
free_masks(desc);
kfree(desc->kstat_irqs);
free_percpu(desc->kstat_irqs);
kfree(desc);
}
@ -234,7 +236,6 @@ struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
}
};
static unsigned int kstat_irqs_all[NR_IRQS][NR_CPUS];
int __init early_irq_init(void)
{
int count, i, node = first_online_node;
@ -250,7 +251,8 @@ int __init early_irq_init(void)
for (i = 0; i < count; i++) {
desc[i].irq_data.irq = i;
desc[i].irq_data.chip = &no_irq_chip;
desc[i].kstat_irqs = kstat_irqs_all[i];
/* TODO : do this allocation on-demand ... */
desc[i].kstat_irqs = alloc_percpu(unsigned int);
alloc_masks(desc + i, GFP_KERNEL, node);
desc_smp_init(desc + i, node);
lockdep_set_class(&desc[i].lock, &irq_desc_lock_class);
@ -275,6 +277,22 @@ static void free_desc(unsigned int irq)
static inline int alloc_descs(unsigned int start, unsigned int cnt, int node)
{
#if defined(CONFIG_KSTAT_IRQS_ONDEMAND)
struct irq_desc *desc;
unsigned int i;
for (i = 0; i < cnt; i++) {
desc = irq_to_desc(start + i);
if (desc && !desc->kstat_irqs) {
unsigned int __percpu *stats = alloc_percpu(unsigned int);
if (!stats)
return -1;
if (cmpxchg(&desc->kstat_irqs, NULL, stats) != NULL)
free_percpu(stats);
}
}
#endif
return start;
}
#endif /* !CONFIG_SPARSE_IRQ */
@ -391,7 +409,9 @@ void dynamic_irq_cleanup(unsigned int irq)
unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
{
struct irq_desc *desc = irq_to_desc(irq);
return desc ? desc->kstat_irqs[cpu] : 0;
return desc && desc->kstat_irqs ?
*per_cpu_ptr(desc->kstat_irqs, cpu) : 0;
}
#ifdef CONFIG_GENERIC_HARDIRQS
@ -401,10 +421,10 @@ unsigned int kstat_irqs(unsigned int irq)
int cpu;
int sum = 0;
if (!desc)
if (!desc || !desc->kstat_irqs)
return 0;
for_each_possible_cpu(cpu)
sum += desc->kstat_irqs[cpu];
sum += *per_cpu_ptr(desc->kstat_irqs, cpu);
return sum;
}
#endif /* CONFIG_GENERIC_HARDIRQS */