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@mielke.cc/markm@ncf.ca/markm(a)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/