[Bf-committers] Re: Strange rendering speed

GSR - FR bf-committers@blender.org
Sat, 10 Jul 2004 20:13:33 +0200


bart@neeneenee.de (2004-07-10 at 1246.46 +0200):
> I did some rendering speed tests on Win2K with a scene of five textured 
> monkeys and color background (nothing more):
> 
> - in Blender itself took 41.70 sec.
> - in background (commandline option -b) with normal task priority
> 	took 43.26
> - and same above but highest task priority took 43.28
> 
> Questions:
> - why is background rendering always slower then normal rendering ?

Does not MSWindows give a longer time slice to foreground processes?
So even if they require the same comparable time, the foreground
process does less context switches, which take time, even if it is to
put the same process again in the CPU.

> - why has canging the priority of the blender task no effect of
> 	rendering speed?

Priority is about which is more important when the CPU has to be
shared. So "speed" (which process will manage to end sooner) will be
affected when many processes are fighting for the CPU, but never make
your CPU faster, neither great effect when there is only one process
wanting to use CPU all the time (maybe this is your case?).

> - Many people told me that Blender on Linux renders 2.5 times faster
> 	then on windows. True? And why?

A bit excesive example, more info about what was done would be
required to figure what really happened. Different compilers,
different set of programs running, different scheduling and
swapping... everything can contribute to the differences.

GSR