heavy load with xcaverot

[Mark Shinwell]

On Mon, May 01, 2000 at 10:37:35PM +0200, Roger Schuster wrote:
> Hi folks, 
> 
> I just tested the new xcaverot from survex 0.93 on a Linux machine and I
> am wondring about the very heavy load this produces on my box. If the
> automatical "rotate" menu item is selected the system load goes up to
> 97 %! The mouse pointer is jumping across the screen and also the
> rotation of the cave is very jerking. 
> 
> "Top" shows that most of the system load isn't caused by xcaverot
> itself but by X11. 
> 
> If the rotation item is not selected the load is low at around 2 %. 
> 
> The machine is a 450 MHz K6-III with an accelerated X-Server. 
> 
> What's going wrong? 

Nothing.  Linux scheduling is based on a system which results in the CPU being
distributed among the processes ready to run, and Xcaverot is written in such a
way that it will produce high load when rotating the cave.  The high CPU usage
for the X server is due to the fact that the server is being hammered with
requests.  On a single processor machine you will have an enormous amount of
context switches between the X server and Xcaverot, which will also slow things
down.

Xcaverot is unfortunately useless at drawing surveys efficiently.

If you upgrade to XFree86 v4.0 you will see significantly improved graphics
performance and correspondingly lower loads.

The aven package operates much faster (although ideally still needs XFree86
4.0, as previous releases of that are slow), although will still at the moment
cause high loads when rotating.  I intend to work on this when I finish my
exams in June.

Mark

-- 
Mark Shinwell  -- President, Cambridge University Caving Club
Queens' College, Cambridge, UK
Mail: mrs30@cam.ac.uk   Web: http://mrs30.quns.cam.ac.uk