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

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Date:	Mon, 17 Aug 2009 07:12:36 +0100 (BST)
From:	Michael Abbott <michael@...neidae.co.uk>
To:	Amerigo Wang <xiyou.wangcong@...il.com>
cc:	Jan Engelhardt <jengelh@...ozas.de>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Re: /proc/uptime idle counter remains at 0

On Mon, 17 Aug 2009, Amerigo Wang wrote:
> On Fri, Aug 14, 2009 at 01:18:08PM +0100, Michael Abbott wrote:
> >commit 6d67e34f45a92f347388e35bd84bf0361e660d3b
> >Author: Michael Abbott <michael.abbott@...mond.ac.uk>
> >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@...mond.ac.uk>
> >
> >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.

I'm sorry?  Are you sure?  Here is what fs/proc/stat.c has to say:

#ifndef arch_idle_time
#define arch_idle_time(cpu) 0
#endif
...
		idle = cputime64_add(idle, arch_idle_time(i));


I think what you're actually saying is the #ifdef can be moved to 
somewhere where it can be easily missed.  For this very reason, I'd rather 
be more explicit about it.


> >+	}
> >+	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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