debian faster than gentoo

kraylus · l33t Joined: 07 Jun 2002 Posts: 648 Location: ft.worth.tx

got this on my local lug mailing list. what's your take on it, guys?

TPC · Posted: Wed Nov 05, 2003 1:26 am Post subject:

Debian is faster for some uses. On my fast laptop Gentoo is faster than Debian, but on my old P133 Gentoo runs so slow that I can't stand it, while it runs Debian without any problems.

chrispy · Apprentice Joined: 10 Nov 2002 Posts: 228 Location: Tokyo

Well, it just proves that :
1-gcc still has room for improvements
2-CFLAGS over-optimization is not the key to faster programs
3-"random" CFLAGS set because "they sound cool" usually make the binaries bigger, and if the code is badly written, can make the binaries a lot slower.

Yes, I believe the debian guys chose the compilation options very carefully because they have a lot of experience. But we do not know what cflags the guy used, which version of GCC. etc, etc...
A badly setup gentoo system, even on a fast cpu, will noticeably be slower than a carefully cooked binary distro.

avenj · Posted: Wed Nov 05, 2003 1:41 am Post subject:

-O3 can cause significant decreases in speed. This is especially true on older systems.

On my i686 systems, I use:
-O2 -pipe -march=i686 -finline-functions -finline-limit=800

RedBeard0531 · Guru Joined: 21 Sep 2002 Posts: 415 Location: maryland

I find -Os to work quite well. It is much faster than -O3 and save lots of space over -O2. Several people have had similar experiances.
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MatzeOne · Posted: Wed Nov 05, 2003 4:39 am Post subject:

nbensa · Posted: Wed Nov 05, 2003 4:57 am Post subject:

Lovechild · Posted: Wed Nov 05, 2003 7:50 am Post subject:

I have my system on -march=athlon-xp -O -pipe and it's no slower than my uber optimized Gentoo system was - of course it's freebsd so it's kinda hard to compare the two.

avenj · Posted: Wed Nov 05, 2003 8:15 am Post subject:

"Optimize smarter, not harder"

beejay · Posted: Wed Nov 05, 2003 8:56 am Post subject:

Before I say anything else : I am a persuaded user of Gentoo...

...but on my Notebook Gentoo really is quite slow. I have a FreeBSD on a 2nd partition and it really runs faster. The Notebook is not throttled, and my CFLAGS still are the original CFLAGS from the P4-LiveCD. However the reason could also be that I chose XFS as I did on my Desktop - but I had really bad experiences with Reiser and I still do not have enough trust in ext3.

A lot of (new) Gentooists are too fascinated by the ability to set up Compiler-Options and I'm sure that a lot of them exaggerate optimization.
What about example-lines in make.conf, say two for every CPU (one for konservative optimization and one for harder [but not exaggerate] optimization) ?
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Mystilleef · Guru Joined: 27 Apr 2003 Posts: 561 Location: Earth

I've noticed a lot of gentoo users choose optimization flags without researching them thoroughly. On several occassions I've seen people post flags on this forums that could essentially ruin their system all in the name of speed. With a little bit of reading (man/info gcc) and a little bit of common sense you could get an extremely optimized system. I see people thinking the more flags they have in make.conf the more l33t their system will be. Well, that's false.

avenj · Posted: Wed Nov 05, 2003 4:39 pm Post subject:

Azaghal · Tux's lil' helper Joined: 02 May 2003 Posts: 103

-Os seems to be 'hot' now.

Everyone seems to have a different view on cflags, even while I get the impression that some ppl think it will make huge differences. Gentoo-ers seem to be very eager at falling back to excuses like "he had his cflags wrong" when someone dares to suggest that Gentoo maybe isn't that 'super fast' at all.

Did anyone ever really bother researching this topic, like comparing different flags for different applications, and having hard numbers in stuff like launch times, etc.

I'm not trying to troll here, but I've yet to see the first proof for claims like "-Os is so much faster than -O3, I can really feel the 10 ms difference it makes when starting the application!" or "my system is 100% optimized, it's so much faster than distro X, I have -fblablabla -omit balblalba -somel33tflag -somedebuggingflagthatsoundscool -O3 -pipe -s -l33t"........
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Mystilleef · Guru Joined: 27 Apr 2003 Posts: 561 Location: Earth

Azaghal · Tux's lil' helper Joined: 02 May 2003 Posts: 103

professorn · Posted: Wed Nov 05, 2003 8:10 pm Post subject:

Probably depends on code too =/

slarti` · Retired Dev Joined: 20 Sep 2003 Posts: 376 Location: UK

Yes, I agree with Azaghal. I doubt very much that most CFLAGS make a huge difference. Obviously some do, but many long and aggressive flags are just over-optimizing and making things slower.

It makes me laugh a bit when people still using 2.4 kernels come up with some huge list of their CFLAGS.. I tell them to upgrade to 2.6 and then notice the difference

BTW, I read an article on linmag.au put forward to me by some Debian users on an IRC channel a while ago. It gave benchmarks for starting OOWriter, performing an operation in GIMP, and one or two other things which I can't remember (long time ago). Gentoo came up often 10x worse than Debian, and Mandrake of all things.. I still deeply question what CFLAGS they were using however... so yes, a knowledge of CFLAGS (something I'm sadly missing

) is important for getting the most out of Gentoo, until you have some really decent CFLAGS you can't claim to have any real speed boost over xyz distro.
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Mystilleef · Guru Joined: 27 Apr 2003 Posts: 561 Location: Earth

Evangelion · Posted: Thu Nov 06, 2003 7:44 am Post subject:

ed0n · Posted: Thu Nov 06, 2003 12:57 pm Post subject:

shm · Posted: Fri Nov 07, 2003 9:21 pm Post subject:

Very few people using gentoo optimize with -O3 anymore.. this guy is just a dumbass.
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hensan · l33t Joined: 26 Jun 2003 Posts: 868 Location: Sweden

ozonator · Posted: Sat Nov 08, 2003 5:48 am Post subject:

Okay, I know this is highly unscientific, and based mostly on my perception of how fast things are (haven't got enough time to do thorough benchmarking), but this thread and the original story from DWN inspired me to do a little experimenting. On my Duron 1200 machine (a little over a year old, Asus A7V266-C, 256 MB DDR266 RAM, 7200 RPM disk), my glibc had been installed with gcc 3.2.3, with these CFLAGS, which I'd happily been using for a while: "-O3 -pipe -march=athlon-xp -mmmx -msse -m3dnow -mfpmath=sse -fforce-addr -fomit-frame-pointer -funroll-loops -foptimize-sibling-calls -fstack-protector" After reading a bit more about optimization in these forums and elsewhere on the web, the message of "smarter, not harder" optimization sunk in. I decided to try these CFLAGS: "-O2 -s -pipe -march=athlon-xp -mmmx -msse -m3dnow -mfpmath=sse -fforce-addr -fomit-frame-pointer -foptimize-sibling-calls -fstack-protector" -- in other words, switch -O3 to -O2, drop -funroll-loops, and add -s.

Then, some recompiling: first, glibc (2.3.2-r1, latest unmasked for x86). After that, I opened a few apps that I was sure I hadn't opened since my last reboot -- dillo, jpilot, rox, among others -- and was pleasantly surprised: it did seem snappier than I remembered it being before, at least in opening. Remember, I said this wouldn't be a scientific test, just a perceptual one, but still -- these apps opened almost instantly, and I remembered them taking at least a little bit of time before.

So, I decided to recompile gcc, binutils, and some of my frequently used apps. With only a few exceptions, I noticed that each binary size is notably smaller. Some examples, in bytes: aterm, 164820 -> 125492; dillo, 407940 -> 340808; gpg, 820940 -> 698864. Some bigger ones: gvim, 2497236 -> 2121300; gs, 3970960 -> 3363988; abiword, 4423616 -> 4106464; and the biggest change, gnumeric, 8799965 -> 3552960. :!:

All seemed snappier starting up, particularly those with large binary sizes, as -Os advocates already know. Once loaded, they're just as fast as I remember them. Again, this is not scientific, but I notice a significant enough change for me to think there's a difference, and to be pleased. And, -O2 certainly does quite a bit to reduce binary size, along with dropping -funroll-loops and adding -s.

This got me thinking some more, so I decided to do another test, still unscientific, but one less reliant on my perception alone: convert a PDF version of my doctoral dissertation to postscript (mostly text in a PDF created by pdflatex; the file is 785752 bytes long, a size that shouldn't tax my disk or RAM much), and see how long it takes with each optimization: "time pdf2ps test.pdf O<level>.ps", where <level> is the optimization level used to compile ghostscript (pdf2ps is a script that calls gs). The ebuild involved is ghostscript-7.05.6-r3, which provides gs and pdf2ps. Conditions: each test was run with the glibc that I had re-compiled with -O2; the -O3 test was run with my original CFLAGS quoted above, since they represented my initial (untest, perhaps more naive) thoughts about optimization. Each run was done with lots of free RAM (no swapping needed), and no other CPU load. Also, I timed the results of the first run of each freshly-compiled binary (i.e., to reduce the effects of cacheing, and thus maybe give a better sense of load + execution time).

Results:

siti · Posted: Sat Nov 08, 2003 7:28 am Post subject:

ozonator: On a side note I have read that you make Propolice ineffective when enabling -O3

sindre · Guru Joined: 01 Nov 2002 Posts: 315 Location: Norway

Just wondering, will you get a performance hit if you use propolice?