Messages in this thread Patch in this message | | | Date | Sat, 14 Jan 2012 00:01:01 +0000 | From | Russell King - ARM Linux <> | Subject | [BUG] vmstat reports no interrupts |
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Running a recent kernel, I'm seeing no interrupt activity being reported by vmstat on my platforms. Investigating, it seems to be caused by this patch merged during the current merge window:
commit 3292beb340c76884427faa1f5d6085719477d889 Author: Glauber Costa <glommer@parallels.com> Date: Mon Nov 28 14:45:17 2011 -0200
sched/accounting: Change cpustat fields to an array
This patch changes fields in cpustat from a structure, to an u64 array. Math gets easier, and the code is more flexible.
Signed-off-by: Glauber Costa <glommer@parallels.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Tuner <pjt@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1322498719-2255-2-git-send-email-glommer@parallels.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch modifies show_stat() thusly:
u64 sum = 0;
for_each_possible_cpu(i) { ... - sum += kstat_cpu_irqs_sum(i); - sum += arch_irq_stat_cpu(i);
where 'sum' is the first value displayed on /proc/stat's intr line. However, this file still contains:
#ifndef arch_irq_stat_cpu #define arch_irq_stat_cpu(cpu) 0 #endif #ifndef arch_irq_stat #define arch_irq_stat() 0 #endif #ifndef arch_idle_time #define arch_idle_time(cpu) 0 #endif
at the top, and otherwise doesn't reference arch_irq_stat_cpu() anymore.
Although x86 (and only x86) implements arch_irq_stat(), this doesn't return the total number of interrupts on the system. Therefore, I conclude that the same bug that I'm seeing on ARM should be visible on every other arch, including x86.
I think this commit wasn't meant to delete these. The patch below restores vmstat's original behaviour for me. Please confirm this fix and submit upstream.
8<==== From: Russell King <rmk+kernel@arm.linux.org.uk> proc: fix /proc/stat intr sum
Commit 3292beb340c7688 (sched/accounting: Change cpustat fields to an array) deleted the code which provides us with the sum of all interrupts in the system, causing vmstat to report zero interrupts occuring in the system. Fix this by restoring the code.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Tested-by: Russell King <rmk+kernel@arm.linux.org.uk> [on ARM] --- fs/proc/stat.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/fs/proc/stat.c b/fs/proc/stat.c index d76ca6a..121f77c 100644 --- a/fs/proc/stat.c +++ b/fs/proc/stat.c @@ -77,6 +77,8 @@ static int show_stat(struct seq_file *p, void *v) steal += kcpustat_cpu(i).cpustat[CPUTIME_STEAL]; guest += kcpustat_cpu(i).cpustat[CPUTIME_GUEST]; guest_nice += kcpustat_cpu(i).cpustat[CPUTIME_GUEST_NICE]; + sum += kstat_cpu_irqs_sum(i); + sum += arch_irq_stat_cpu(i); for (j = 0; j < NR_SOFTIRQS; j++) { unsigned int softirq_stat = kstat_softirqs_cpu(j, i);
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