Re: [PATCH] Re: /proc/uptime idle counter remains at 0
From: Andrew Morton
Date: Wed Sep 09 2009 - 02:05:00 EST
On 2009年8月14日 13:18:08 +0100 (BST) Michael Abbott <michael@xxxxxxxxxxxxxxx> wrote:
>
Reviving this:
>
>
On Sat, 9 May 2009, Jan Engelhardt wrote:
>
> starting from v2.6.28-4930-g79741dd lasting thru at least v2.6.29.1,
>
> the second field of /proc/uptime always shows 0.00. This happens for
>
> both the typical i386 (my case) and on an ARM (according to Michael,
>
> cc'ed).
>
>
>
> >From the commit log of 79741dd:
>
>
>
> """The cpu time spent by the idle process actually doing
>
> something is currently accounted as idle time. This is plain
>
> wrong, the architectures that support VIRT_CPU_ACCOUNTING=y
>
> can do better: distinguish between the time spent doing
>
> nothing and the time spent by idle doing work. The first is
>
> accounted with account_idle_time and the second with
>
> account_system_time."""
>
>
>
> Citing Michael from our irc conversation:
>
>
>
> """the writer[committer] [says] that [the] idle process time
>
> isn't really idle time ... but that's all that /proc/uptime
>
> looks at. I guess fs/proc/uptime.c needs to catch up."""
>
>
>
> So, were the updates to uptime.c missed, or do we now live on with
>
> /proc/uptime constantly having 0?
>
>
My previous patch seems to have run into the sand. It every so nearly got
>
pulled into mainstream as far as I can tell, but didn't seem to make it;
>
no idea what happened.
>
>
So here we go again:
>
Imagine my surprise to find a version of this patch lurking in Martin's
tree since June 22. It's a regression fix!
Johan, does this patch help with the regression you reported in
http://bugzilla.kernel.org/show_bug.cgi?id=14131 ?
Thanks.
commit 27bf8712477db47c891e6198000c985631cd18de
Author: Michael Abbott <michael.abbott@xxxxxxxxxxxxx>
AuthorDate: Mon Jun 22 12:19:25 2009 +0200
Commit: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
CommitDate: Mon Jun 22 12:20:44 2009 +0200
[PATCH] Fix idle time field in /proc/uptime
Git commit 79741dd changes idle cputime accounting, but unfortunately
the /proc/uptime file hasn't caught up. Here the idle time calculation
from /proc/stat is copied over.
Signed-off-by: Michael Abbott <michael.abbott@xxxxxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
diff --git a/fs/proc/uptime.c b/fs/proc/uptime.c
index 0c10a0b..766b1d4 100644
--- a/fs/proc/uptime.c
+++ b/fs/proc/uptime.c
@@ -4,13 +4,18 @@
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/time.h>
+#include <linux/kernel_stat.h>
#include <asm/cputime.h>
static int uptime_proc_show(struct seq_file *m, void *v)
{
struct timespec uptime;
struct timespec idle;
- cputime_t idletime = cputime_add(init_task.utime, init_task.stime);
+ int i;
+ cputime_t idletime = cputime_zero;
+
+ for_each_possible_cpu(i)
+ idletime = cputime64_add(idletime, kstat_cpu(i).cpustat.idle);
do_posix_clock_monotonic_gettime(&uptime);
monotonic_to_bootbased(&uptime);
--
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