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authorEric Dumazet <eric.dumazet@gmail.com>2011-01-13 15:45:38 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 17:32:31 -0800
commit6c9ae009b298753a3baf71298d676a68b5a10c8f (patch)
tree95a7e4ca54fe8e96c95cedd4e8d6450659015212 /kernel
parent558bbb2fc75fd9676e07e347c021865e326c56db (diff)
downloadlinux-linaro-precise-6c9ae009b298753a3baf71298d676a68b5a10c8f.tar.gz
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/irq/irqdesc.c40
1 files changed, 30 insertions, 10 deletions
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 9988d03797f..282f20230e6 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -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 */