Safe (but quick) GCC settings on a PC64 with 5.3?
Kirk Strauser
kirk at strauser.com
Mon Dec 13 09:31:03 PST 2004
I just upgraded a little PC64 from FreeBSD 4.10 to 5.3 via the installer
ISO. First, I'd like to send my gratitude and appreciation to everyone who
helped on the Alpha port; the upgrade was a piece of cake and worked
perfectly from the first boot.
Anyway, I'm planning to rebuild all of my ports to take advantage of GCC's
new optimizations (versus the old 2.95 version they'd been previously built
with) and the kernel to try to wring a little more performance out of this
small system whose dmesg starts with:
Copyright (c) 1992-2004 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD 5.3-STABLE #0: Sun Dec 12 22:31:54 CST 2004
root at gopher.honeypot.net:/usr/obj/usr/src/sys/NEW_GOPHER
EB64+
Digital AlphaPC 64 274 MHz, 274MHz
8192 byte page size, 1 processor.
CPU: EV45 (21064A) major=6 minor=2
OSF PAL rev: 0x100040002012d
real memory = 266346496 (254 MB)
avail memory = 250544128 (238 MB)
apecs0: <DECchip 21072 Core Logic chipset>
I currently have these in my /etc/make.conf:
CPUTYPE=ev45
CFLAGS= -O -pipe -mieee
COPTFLAGS= -O -pipe
I have *no* desire to make an unstable system in an attempt to squeeze out
that last 0.2% of performance. On the other hand, this box isn't exactly a
speed demon and every little bit can make a noticeable difference. If I
can get an extra 10% at the cost of a lengthy recompile, I'll jump at the
chance.
I have much more experience with x86 and Sparc systems than Alpha, and I'm
not really sure what else I should or could have in there. I've read the
"DEC Alpha Options" section of GCC manual, but I don't have the experience
to know whether things like '-mno-soft-float' are good or bad, or whether I
should be mucking around with '-mmemory-latency'. This is where I could
really use a bit of guidance.
Many thanks!
--
Kirk Strauser
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