Re: CPU load

[Con Kolivas]

On Monday 12 February 2007 16:55, Stephen Rothwell wrote:
> On Mon, 12 Feb 2007 16:44:22 +1100 "Con Kolivas" <kernel@xxxxxxxxxxx> wrote:
> > The kernel looks at what is using cpu _only_ during the timer
> > interrupt. Which means if your HZ is 1000 it looks at what is running
> > at precisely the moment those 1000 timer ticks occur. It is
> > theoretically possible using this measurement system to use >99% cpu
> > and record 0 usage if you time your cpu usage properly. It gets even
> > more inaccurate at lower HZ values for the same reason.
>
> That is not true on all architecures, some do more accurate accounting by
> recording the times at user/kernel/interrupt transitions ...

Indeed. It's certainly the way the common more boring pc architectures do it 
though.

-- 
-ck
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/