Brian Beesley wrote:
On Tuesday 19 July 2005 23:54, John R Pierce wrote:
Is there a prime.ini parameter for CPU affinity? I run the mprime on
Linux and haven't come across such a value yet.
it was my understanding that the linux kernel didn't even support
per-process CPU affinity until 2.6.
And it's my understanding that - apart from hyperthreading and some types of
architecture where memory is partitioned by processor core - it's usually
best to let the process scheduler make its own mind up - linux process
schedulers usually try hard to keep threads running in the same core anyway.
The point being that if you rely on fixed affinity and some idiot tries to
run two compute-bound processes on the same core then you can end up with a
system with a long compute queue but with significant amounts of totally
wasted cpu cycles.
however, something like mprime/prime95 is a special case. as each CPU has its
own cache, and mprime/prime95 is heavily optimized for cache usage, having it
flip between processors will require a lot of extra cache reloading, as well as
requiring constant floating point state save/reloads
I'm pretty sure most x86 multiprocessor systems are smart enough to postpone
saving/restoring the FPU state until a process actually tries to use it...
since most processes don't do ANY FPU or only occasionally a little, this means
if a CPU is sharing between prime and non-FP job, the floating point state
doesn't need to be saved/restored at all, as the FPU state is quite large, this
saves a LOT of cycles..
_______________________________________________
Prime mailing list
[email protected]
http://hogranch.com/mailman/listinfo/prime
