| 1 |
MAL wrote: |
| 2 |
> Koby Boy wrote: |
| 3 |
> |
| 4 |
>> On Tue, 2003-05-06 at 03:24, eNTi wrote: |
| 5 |
>> |
| 6 |
>>> CFLAGS="-mcpu=athlon-xp -O3 -pipe -m3dnow -msse -mmmx -Wall |
| 7 |
>>> -fomit-frame-pointer" / CHOST="i686-pc-linux-gnu" |
| 8 |
>> |
| 9 |
>> |
| 10 |
>> I've got an Athon-XP 2400 (2 GHz) but I've over clocked it to the |
| 11 |
>> equivalent of an Athlon-XP 2600 (2.2GHz). My CFLAGS look like this: |
| 12 |
>> |
| 13 |
>> CFLAGS="-mcpu=athlon-xp -march=athlon-xp -O3 -fforce-addr |
| 14 |
>> -fomit-frame-pointer -funroll-loops -frerun-cse-after-loop |
| 15 |
>> -frerun-loop-opt -falign-functions=4 -foptimize-sibling-calls |
| 16 |
>> -fexpensive-optimizations -pipe -m3dnow -mmmx -msse -mfpmath=sse,387" |
| 17 |
> |
| 18 |
> |
| 19 |
> -march=athlon-xp implies: |
| 20 |
> -mcpu=athlon-xp |
| 21 |
> |
| 22 |
> -march=athlon-xp implies: |
| 23 |
> -m3dnow |
| 24 |
> -mmmx |
| 25 |
> -msse |
| 26 |
> |
| 27 |
> -O3 implies -O2 which implies: |
| 28 |
> -frerun-loop-opt |
| 29 |
> -frerun-cse-after-loop |
| 30 |
> -frerun-loop-opt |
| 31 |
> -falign-functions |
| 32 |
> -fexpensive-optimizations |
| 33 |
> |
| 34 |
> -mfpmath=sse,387 is still unstable.. asking for trouble! |
| 35 |
> |
| 36 |
> Lastly, many people have expressed that -funroll-loops slows down more |
| 37 |
> code than it speeds up. |
| 38 |
> |
| 39 |
> I'd be surprised if you see much improvement over '-O3 -pipe', in 99% of |
| 40 |
> apps, not worth it's time in debugging broken code :/ |
| 41 |
> |
| 42 |
> man gcc *g* |
| 43 |
> |
| 44 |
> MAL |
| 45 |
> |
| 46 |
> |
| 47 |
> -- |
| 48 |
> gentoo-performance@g.o mailing list |
| 49 |
Actually, mfpmath=sse,387 works for most programs, but it is actually |
| 50 |
slower for me than mfpmath=387 on my Athlon-XP, at least in my |
| 51 |
benchmark, which is lame encoding. -funroll-loops slows it down. |
| 52 |
setting -falign-functions to something bigger than 4 (the default I |
| 53 |
believe) does make a small positive difference. -falign-loops and |
| 54 |
-falign-jumps also should be set to 5 or something like that, for |
| 55 |
optimal speed. |
| 56 |
I also tried -malign-double and -m128bit-long-double, which speed up |
| 57 |
Lame some more, but breaks ABI compatibility and make the code size larger. |
| 58 |
I know that running only Lame isn't the best way to bench, but I think |
| 59 |
that Lame uses a large set of functions, and if Lame runs fast, other |
| 60 |
programs shouldn't be slow. |
| 61 |
As for debugging vs performance, I'm just a person that likes to tweak |
| 62 |
performance to the utmost, and some breakage and debugging just adds to |
| 63 |
the fun I think. |
| 64 |
|
| 65 |
FCA |
| 66 |
|
| 67 |
|
| 68 |
-- |
| 69 |
gentoo-performance@g.o mailing list |
Archives