Re: NetBSD speed curiosities

[John Klos <john%ziaspace.com@localhost>]

On 19/04/14 11:20 PM, Anders Magnusson wrote:

> Suddenly something is added that makes hardclock take 5000 instructions 
> instead.  On the 1MIPS machine we now only have 50% of the CPU left, but 
> on the newer machine we still have 99.9% of the CPU left (== not 
> noticeable). Something like this can only be seen on a really slow 
> machine, it's most likely not possible to find it even with fine-grain 
> profiling on a modern PC.

This would explain the disparities I'm seeing between 4000/30 and 4000/60 
performance:

> The real questions are why is it that Digital got 19105 dhrystones a 
> second on the VLC and and 30120 on the 4000/60, but NetBSD gets 2109 
> (11%) and 16305 (54%) of DEC speeds, and why is the difference between 
> the two so different?

I do have a 4000/90a, but haven't been running it while waiting for some 
replacement SIMM sockets (some pins have become corroded). Three data 
points on one version of the OS isn't much, so I'm curious about what 
others have.

Reducing overhead doesn't just help the VAX port - I'm building embedded 
products and one of the platforms may be a 400 MHz MIPS system with 16 
megs of memory, in which case every little bit counts.

John