Re: OFFTOPIC: Regarding NT vs Linux
Adam Fritzler (afritz@iname.com)
Sun, 21 Sep 1997 10:57:34 -0700
At 08:56 PM 9/21/97 +1100, Russell Coker - mailing lists account wrote:
>>InternetWeek did an article on different OS's acting as web servers a
>>couple of weeks ago. NT actually got slower with a second CPU.
>
> This is not a surprise. It's well known that machines which are IO
>bound can often suffer greatly from having too many CPUs. When I was at
>university one of the UNIX servers was taken from 8 CPUs to 2 to improve
>it's network and file performance. The machine was only allowed to have 2
>CPUs because some people were doing parallel processing research on it,
>otherwise it would have gone down to 1 CPU.
> If your OS is spending all it's time processing interrupts/DMA etc then
>having multiple CPUs fighting over this is unlikely to improve performance,
>even if interrupts can be processed on multiple CPUs. If only 1 CPU can
>handle interrupts and it has to ackquire global locks to do some of it's
>work then things may be really bad.
This was the purpose of the NUMA architecture: to actually have a
performance _increase_ when adding more processors. Each CPU has it's own
memory, plus the machine's main memory. This decreased the amount of
clutter on the main address bus and increased available bandwidth to more
useful things. It works, but it's very expensive.
( Adam Fritzler afritz@iname.com )
http://afritz.base.org/
Linux/mac68k: (Linux for 68k Macintoshes)
http://www.maclinux.org
http://afritz.base.org/linux-mac68k/