From: Vahid Moghaddasi (sunman@ureach.com)
Date: Mon Feb 02 2004 - 22:39:56 EST
Hi,
Thanks to the following who replied, most people mentioned that
it is not
matter of lying or not, it is just the way %CPU utilization is
calculated on
Sun systems.
Darren Dunham
Matthew Stier
Thomas M. Payerle
joe_fletcher@btconnect.com
Eric Voisard
Here is Jay Lessert's answer:
On Sun, Feb 01, 2004 at 10:30:46PM -0500, Vahid Moghaddasi
wrote:
> Hi,
> Is this correct that to get the real CPU usage of a process,
we
> will have to multiply the %CPU utilization shown by top or
> prstat by the number of CPU's in the system?
That is correct.
> For example, if
> there are 10 CPU's in a system and top shows lets say gzip is
> using %5, that means 5x10=%50 of one CPU.
Correct.
> I understand top not telling the correct usage on Solaris (it
OK
> on hp-ux) but why prstat is lying?
It is not lying, that is the way it is intended to work, theory
being that:
1) This is the % system utilization regardless of # of CPU's
2) Single processes can be multi-threaded; in your 10-cpu
example,
a single process with 5 threads active could show 50%
utilization.
As you, I would prefer that process to show 500% utilization,
and the very first Sun MP kernels worked that way (4.1.x), but
that is not the way it works now. Perhaps it is a SysV thing.
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