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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 /fs/proc/stat.c
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 'fs/proc/stat.c')
-rw-r--r--fs/proc/stat.c10
1 files changed, 2 insertions, 8 deletions
diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index b80c620565b..e15a19c93ba 100644
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -31,7 +31,6 @@ static int show_stat(struct seq_file *p, void *v)
u64 sum_softirq = 0;
unsigned int per_softirq_sums[NR_SOFTIRQS] = {0};
struct timespec boottime;
- unsigned int per_irq_sum;
user = nice = system = idle = iowait =
irq = softirq = steal = cputime64_zero;
@@ -108,13 +107,8 @@ static int show_stat(struct seq_file *p, void *v)
seq_printf(p, "intr %llu", (unsigned long long)sum);
/* sum again ? it could be updated? */
- for_each_irq_nr(j) {
- per_irq_sum = 0;
- for_each_possible_cpu(i)
- per_irq_sum += kstat_irqs_cpu(j, i);
-
- seq_printf(p, " %u", per_irq_sum);
- }
+ for_each_irq_nr(j)
+ seq_printf(p, " %u", kstat_irqs(j));
seq_printf(p,
"\nctxt %llu\n"