path: root/kernel
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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2010-10-27 15:34:15 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-27 18:03:13 -0700
commit478735e38887077ac77a9756121b6ce0cb956e2f (patch)
tree7b42110f71b1711f56cbbc0a01f00894b221337d /kernel
parentf2c66cd8eeddedb440f33bc0f5cec1ed7ae376cb (diff)
/proc/stat: fix scalability of irq sum of all cpu
In /proc/stat, the number of per-IRQ event is shown by making a sum each irq's events on all cpus. But we can make use of kstat_irqs(). kstat_irqs() do the same calculation, If !CONFIG_GENERIC_HARDIRQ, it's not a big cost. (Both of the number of cpus and irqs are small.) If a system is very big and CONFIG_GENERIC_HARDIRQ, it does for_each_irq() for_each_cpu() - look up a radix tree - read desc->irq_stat[cpu] This seems not efficient. This patch adds kstat_irqs() for CONFIG_GENRIC_HARDIRQ and change the calculation as for_each_irq() look up radix tree for_each_cpu() - read desc->irq_stat[cpu] This reduces cost. A test on (4096cpusp, 256 nodes, 4592 irqs) host (by Jack Steiner) %time cat /proc/stat > /dev/null Before Patch: 2.459 sec After Patch : .561 sec [akpm@linux-foundation.org: unexport kstat_irqs, coding-style tweaks] [akpm@linux-foundation.org: fix unused variable 'per_irq_sum'] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Tested-by: Jack Steiner <steiner@sgi.com> Acked-by: Jack Steiner <steiner@sgi.com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Ingo Molnar <mingo@elte.hu> 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')
1 files changed, 15 insertions, 0 deletions
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 9d917ff7267..9988d03797f 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -393,3 +393,18 @@ 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;
+unsigned int kstat_irqs(unsigned int irq)
+ struct irq_desc *desc = irq_to_desc(irq);
+ int cpu;
+ int sum = 0;
+ if (!desc)
+ return 0;
+ for_each_possible_cpu(cpu)
+ sum += desc->kstat_irqs[cpu];
+ return sum;