Re: [PATCH] Re: /proc/uptime idle counter remains at 0

[Amerigo Wang]

On Fri, Aug 14, 2009 at 01:18:08PM +0100, Michael Abbott 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:
>
>commit 6d67e34f45a92f347388e35bd84bf0361e660d3b
>Author: Michael Abbott <michael.abbott@xxxxxxxxxxxxx>
>Date:   Mon May 11 07:14:19 2009 +0100
>
>    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.  Further changes from commit e1c8053
>    are also included in this fix.
>    
>    Signed-off-by: Michael Abbott <michael.abbott@xxxxxxxxxxxxx>
>
>diff --git a/fs/proc/uptime.c b/fs/proc/uptime.c
>index 0c10a0b..be286b4 100644
>--- a/fs/proc/uptime.c
>+++ b/fs/proc/uptime.c
>@@ -4,22 +4,32 @@
> #include <linux/sched.h>
> #include <linux/seq_file.h>
> #include <linux/time.h>
>+#include <linux/kernel_stat.h>
> #include <asm/cputime.h>
>+#include <asm/div64.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;
>+	cputime64_t idle = cputime64_zero;
>+	unsigned long int idle_mod;
>+
>+	for_each_possible_cpu(i) {
>+		idle = cputime64_add(idle, kstat_cpu(i).cpustat.idle);
>+#ifdef arch_idle_time
>+		idle = cputime64_add(idle, arch_idle_time(i));
>+#endif


This ugly #ifdef can be removed, check fs/proc/stat.c.

Thanks.


>+	}
>+	idle = cputime64_to_clock_t(idle);
>+	idle_mod = do_div(idle, 100);
> 
> 	do_posix_clock_monotonic_gettime(&uptime);
> 	monotonic_to_bootbased(&uptime);
>-	cputime_to_timespec(idletime, &idle);
>-	seq_printf(m, "%lu.%02lu %lu.%02lu\n",
>+	seq_printf(m, "%lu.%02lu %llu.%02lu\n",
> 			(unsigned long) uptime.tv_sec,
> 			(uptime.tv_nsec / (NSEC_PER_SEC / 100)),
>-			(unsigned long) idle.tv_sec,
>-			(idle.tv_nsec / (NSEC_PER_SEC / 100)));
>+			idle, idle_mod);
> 	return 0;
> }
> 
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