Re: Question about /proc/uptime
From: Oleg Nesterov
Date: Fri Dec 27 2013 - 09:44:28 EST
Add Frederic, I am not sure I understand this correctly.
On 12/25, Rob Landley wrote:
> There are two values here, the first is seconds since boot time (which
> is just elapsed time; at one point it was ajusted for suspend and that
> was revered as confusing).
Hmm, uptime_proc_show() still uses get_monotonic_boottime(), this should
include suspend time?
> The second value isn't documented but looking at fs/proc/uptime.c I
> think it's idle time?
And this cpustat[CPUTIME_IDLE] doesn't match get_idle_time(), I guess
it only counts ticks.
> Except, if yo uadd up the idle time from all
> processors wouldn't you get 4x the uptime on a 4-way SMP system that's
> been idle since boot?
Yes, looks strange.
> Also, is this actual "cpu was on but not doing anything" time, so
> doesn't count suspend as idle?
I think suspend is not counted as idle.
I guess the 2nd value is historical, probably you should use /proc/stat.
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