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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2010-10-27 15:34:13 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-27 18:03:13 -0700
commitf2c66cd8eeddedb440f33bc0f5cec1ed7ae376cb (patch)
tree4b8cfcd2a76652839121707fc2a49b70489ec055 /fs/proc
parent19cd56c48da58bebc3a638e036bcab69469acd27 (diff)
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/proc/stat: scalability of irq num per cpu
/proc/stat shows the total number of all interrupts to each cpu. But when the number of IRQs are very large, it take very long time and 'cat /proc/stat' takes more than 10 secs. This is because sum of all irq events are counted when /proc/stat is read. This patch adds "sum of all irq" counter percpu and reduce read costs. The cost of reading /proc/stat is important because it's used by major applications as 'top', 'ps', 'w', etc.... A test on a mechin (4096cpu, 256 nodes, 4592 irqs) shows %time cat /proc/stat > /dev/null Before Patch: 12.627 sec After Patch: 2.459 sec 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 'fs/proc')
-rw-r--r--fs/proc/stat.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index bf31b03fc27..b80c620565b 100644
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -52,9 +52,7 @@ static int show_stat(struct seq_file *p, void *v)
guest = cputime64_add(guest, kstat_cpu(i).cpustat.guest);
guest_nice = cputime64_add(guest_nice,
kstat_cpu(i).cpustat.guest_nice);
- for_each_irq_nr(j) {
- sum += kstat_irqs_cpu(j, i);
- }
+ sum += kstat_cpu_irqs_sum(i);
sum += arch_irq_stat_cpu(i);
for (j = 0; j < NR_SOFTIRQS; j++) {