svn commit: r198848 - head/bin/ps

Bruce Evans brde at
Thu Nov 12 20:09:19 UTC 2009

On Thu, 12 Nov 2009, M. Warner Losh wrote:

> I'd argue that as we get more and more cores that %CPU will need to
> change.
> If we change it like Bruce suggests, then when we have 1024
> core/thread processors the 'pegged' thread shows up as 0.09% of the
> CPU and likely nothing else shows up at all since the usages are
> diluted by a factor of 1024.

You mean, like I said not to.

> However, for the 'TOP' display, 102400% of the CPU seems like a crazy
> thing to report, even if it is consistent with what other systems
> report for fewer cores going back to 1980's when VMS reported up to
> 200% CPU for the VAX 11/785 on both BSD and VMS.

102400 isn't a very large number.  1M CPUs would give a more interesting
number.  Anyway, displaying %CPUs is the least of the problems in displaying
many threads in top.  top has the same problems as systat -p, but more so.
It wants to display the top active threads, while systat -p only wants to
display the top active threads if they are active enough to be considered
pigs.  You need the 6 metre high terminal to display the 1024 idle threads
for top -SH.  If you only want to display user threads then you will
still need O(ncpu) lines to display enough active ones if all of the CPUs
are actually used.

> Likewise, we have issues with our current TOP display eating up a
> bunch of columns for 55670k of core when 56M would generally give the
> same info to the user (I say generally, because the former is useful
> in watching for memory leaks).
> Maybe we just need to have top offer different views into this data
> for the different needs that people have for it.  A 'detailed' view
> that helps expose even small differences that is useful in
> development, and a 'condensed' version that gives more of the general
> sense of what's going on in the system in a more concise format, but
> might lack some of the details found today.
> Here's where my bikeshed proximity detector starts beeping...

Adding all the different views would take a lot of paint and many would
not like its color.  I just want to avoid changing the standard view
to one that works worse for small configurations.


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