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Message-ID: <1288973210.2882.733.camel@edumazet-laptop>
Date: Fri, 05 Nov 2010 17:06:50 +0100
From: Eric Dumazet <eric.dumazet@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
Christoph Lameter <cl@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
Tejun Heo <tj@...nel.org>, Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v2] 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@...il.com>
Cc: Christoph Lameter <cl@...ux-foundation.org>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: Tejun Heo <tj@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
V2: support for !CONFIG_SPARSE_IRQ
No white space changes.
Question : Is dynamic percpu allocator ready at this stage for all
arches ? The need is NR_IRQS*4 bytes of percpu memory for
!CONFIG_SPARSE_IRQ
diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index 979c68c..6a64c6f 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -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 */
diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index ad54c84..0cce2db 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -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) \
- (kstat_this_cpu.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)
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 9988d03..a789a22 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 */
--
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