Re: layout for top's CPU utilization display

[Tobias Nygren <tnn%NetBSD.org@localhost>]

On Mon, 12 May 2008 07:48:56 -0400
"Greg A. Woods; Planix, Inc." <woods%planix.ca@localhost> wrote:

> I don't really like that layout -- one per line is best, if there must  
> be one line per CPU.
> 
> Two points:
> 
> 1. aspiring to fit useful information, especially about "large"  
> systems, within an 80x24 display is not a useful or laudable goal in  
> these days when mega-pixel displays are practically the minimum.  It's  
> easy to get at least 50 lines with decent character size on even a  
> small laptop display.  I'm not even sure it's worthwhile to try to  
> write code to alternately support a compromised layout like that in  
> case it is detected that the current screen size is too small.
> 
> 2. the one per line layout really is much easier to read I think, i.e.  
> for the eye to be able to see trends and patterns in the data.  Of  
> course ideally a graphical representation is most useful for this  
> purpose.
> 
> Anyway, beyond 4-6 lines it's not very likely that many of us can sum  
> up the total utilization on every update, even if it is only once  
> every 5 seconds.  A more dedicated, and hopefully more graphical,  
> display would be best if the goal is to visualize individual CPU usage  
> (say to verify the fairness of the scheduler and/or the achieved  
> parallelism of the workload).  For the likes of 'top' and 'systat' it  
> is probably best to just give the overall CPU utilization on one line.

I do agree that the multicolumn display does impair readability a bit,
but not that much. One advantage is that it scales to 3 or 4 cols on
120 or 160 character wide displays. On an 80 character display the
multi column layout will only save lines if ncpus >= 4, so for 3 CPUs
or less the current format is preferable. I think graphical displays
are entirely beyond the scope of the utility in question.

A separate cpu monitoring tool is definitely the way to go, but
it doesn't solve the long term problem with top(1), unless we opt to
remove the CPU stat lines entirely.

-Tobias