[tlug] Re: /proc/uptime

[John Fremlin <john@example.com>]

"Nguyen Vu Hung" <vuhung16plus@example.com> writes:
> On Wed, Nov 12, 2008 at 2:34 PM, John Fremlin <john@example.com> wrote:
>> "Nguyen Vu Hung" <vuhung16plus@example.com> writes:
>>> On Wed, Nov 12, 2008 at 12:30 PM, John Fremlin <john@example.com> wrote:
>>>> "Nguyen Vu Hung" <vuhung16plus@example.com> writes
>>>>>         cputime_t idletime = cputime_add(init_task.utime, init_task.stime);
>>>>
>>>> This just adds up how much time (user + system) has been spent in the
>>>> init_task, so how much time has been spent with no actual task running.
>>> On a heavy-load web server which server which serves dozens TB every months
>>> I see:
>
> # I've just read http://kilobug.free.fr/hurd/pres-en/abstract/html/node2.html
> #I know it is for GNU/Hurd so Dr. S. may disagree.
>
>> Why do you think that it is heavily loaded?
> I can hear that my HDD is screaming.

That means the CPUs are probably waiting for the disks.

> My understanding is that: the second number in /proc/uptime indicates
> the time that the kernel has nothing to do in the *kernel
> mode*. Network activities, file systems activities are all in user
> mode so it is nothing to do with /proc/uptime.

No. It indicates the amount of time any one of the cores has nothing to
do.

Look at the top output to see the instantaneous load.

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