P4s, Athlons and bandwidth

Mark Mielke mark at mark.mielke.cc
Wed Aug 13 20:35:32 UTC 2003


The point of the i686 instructions, is that certain key instructions
became available, not that the scheduling is perfect. Have you timed
the benefit of using -mcpu=p4 over -mcpu=i686? Is it really worthwhile?
Or are you just guessing?

I wouldn't mind if a PIII version came with RedHat - but then again, it
is very easy to recompile the kernel for PIII, deselect all the crap
that I don't want, and have an optimal system. I don't need RedHat to
change their distribution to satisfy my whim.

As for GLIBC optimized support for P4 or the latest AMD chips, RedHat
is probably the wrong organization to ask. What is the business case?
I'm sure people on the GLIBC mailing lists would be glad to receive
patches from you that implement proven optimizations...

Just some perspective... :-)
mark

On Wed, Aug 13, 2003 at 10:23:01PM +0200, Jean Francois Martinez wrote:
> Given that most/all of the recent boxes (ie the ones doing the real
> work) are P4s and Athlons it is time RedHat stopped compiling
> with -mcpu=i686 and started optimizing for the P4: -mcpu=p4
> 
> Another point is that there is no such thing like low-level glibc
> functions for the P4 and the Athlon.  The highest targetted
> processor is the PIII.  However documents in AMD's web site show
> that moving data (ie memcpy and friends) can be made several times
> faster if using 3DNow instructions and data prefetching, I gave only
> a cursory glance to the assembler parts of glibc but it didn't look
> like those parts (targetting the PIII) would be even remotely ideal
> for the Athlon.  Same thing about the P4.
> 
> Would it be possible for RedHat to contact those with an interest ie
> AMD/Intel in order to get high-pedrformance assembly versions of those
> low level routines?  Or failing that to have them written by an
> employee?

-- 
mark at mielke.cc/markm at ncf.ca/markm at nortelnetworks.com __________________________
.  .  _  ._  . .   .__    .  . ._. .__ .   . . .__  | Neighbourhood Coder
|\/| |_| |_| |/    |_     |\/|  |  |_  |   |/  |_   | 
|  | | | | \ | \   |__ .  |  | .|. |__ |__ | \ |__  | Ottawa, Ontario, Canada

  One ring to rule them all, one ring to find them, one ring to bring them all
                       and in the darkness bind them...

                           http://mark.mielke.cc/





More information about the test mailing list