Re: Request for testing - top 3.8b1 in the base system

On Sun, Sep 28, 2008 at 9:16 AM, William LeFebvre <bill_at_lefebvre.org> wrote:
> Edwin Groothuis wrote:
>>
>> On Sun, Sep 28, 2008 at 02:09:00AM -0700, Garrett Cooper wrote:
>>>
>>> On Sun, Sep 28, 2008 at 1:14 AM, Alex Keda <admin_at_lissyara.su> wrote:
>>>>
>>>> Some strange. Count running processes not match with system top
>>
>> That has been explained in an email before.
>>
>>> I'm not sure I'm finding an issue, but I do find it interesting that...
>>> 1. It takes a reasonably long amount of time for top to plateau the
>>> WCPU field (approximately 8-10 iterations), whereas ps registering the
>>> WCPU percentage value is almost instantaneous.
>
> Top 3.8 doesn't display WCPU.  It is an antequated measure that is only
> maintained by the kernel so that ps can display it.  It no longer has any
> meaning to the scheduler, so why bother displaying it.
>
>>
>> With ps it takes 10 2 second steps to get the WCPU from 0 to 100,
>> with the new top (which doesn't have WCPU (See Changes file, and
>> the m_freebsd.c file, I don't know of the real reason behind it)
>> anymore) goes from 0 to 100 in 2 2 second steps.
>
> ps shows a decaying average as calculated by the kernel over the past minute
> and recorded in the proc structure.  Top calculates its own average based on
> the difference in cpu time between the last measurement and the current
> measurement.  The output from ps is fine when you want a single snapshot:
> you want it to show information averaged over a long period of time.  Top is
> showing you only what's going on right now, since the last update.  That's
> why percent CPU in top will climb to its final value so quickly.
>
> Bill LeFebvre

Actually, I was trying to say it was the other way around -- WCPU took
a long time in top to climb to its final value where it took a short
period of time with ps. Retrying that though, it appears that I was
flip-flopping my statement and yes it aligns with Bill's.

I still find the averaging discrepancy a bit interesting, but it's
merely a function of how the average is being taken.

-Garrett