Re: [tlug] Re: /proc/uptime

[Edward Middleton <emiddleton@example.com>]

Nguyen Vu Hung wrote:
> On Wed, Nov 12, 2008 at 10:35 PM, John Fremlin <john@example.com> wrote:
>>> 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.
> Is this a good design? I think no. I will replace OR with AND.
> Not every recently applications are SMP aware, and some never is.

Its not an SMP problem, your IO is not fast enough so your CPU is mostly
doing nothing waiting for data.

>> Look at the top output to see the instantaneous load.
> I am running 2.6.18 on a Pen 4 and a Dual Xeon and I observe that
> in put output of "top and press 1", the second CPU( or core in case of Pen 4)
> is idle most of the time, but the first CPU is not: there is always
> some activites
> ( 9x.x% id but not 100%)

How many processes/threads do you have.  If you have only one large
process then soft affinity will try to run it on the same CPU because it
is more efficient then spreading it evenly over both CPUs.

Edward