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For anyone who says compile options don't matter: - The Desian Universe
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deskitty
deskitty
Des
Sun, Jan. 18th, 2009 04:50 pm
For anyone who says compile options don't matter:

I've noticed a HUGE difference in performance between -Os and -O3 with xorg. With compositing turned on (on my crappy Intel 945GM), -Os makes even typing very difficult, to say the least. But I recompiled with -O3 and now X isn't missing a key.

I used to agree with the "compile options don't matter that much" crowd. But I was just proven wrong.

-- Des

Tags:
Current Location: Parents' House
Current Mood: surprised surprised

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oakwind44
oakwind44
Oakwind Softlight
Mon, Jan. 19th, 2009 08:24 am (UTC)

Hmm, from what I've poked around with, I've found that -O[whatever] is one of the biggest program changers out there. So on the one hand, you're quite right, some options do matter. However, anything can be taken to an extreme, and some options (esp. depending upon what your code does / does not do) may not change a gosh darn thing. I think the folks who insist on every little option being checked, cross-checked, compared, and contrasted (with full benchmarking data tables and diagrams, of course) are where the bulk of "the options don't matter" crowd get their fuel.


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deskitty
deskitty
Des
Mon, Jan. 19th, 2009 08:42 am (UTC)

I always thought it came from those who were like "well I tried this, but it didn't copy my file any faster so it must not make any difference".

In fact, I was in that crowd for that reason -- for general-purpose computing (web browsers, office documents, etc.), I/O is probably the bigger bottleneck. But that's becoming less true as visual effects ramp up and crazy people like me rebuild their entire system for the sake of a single compiler option. ;P

Really, though, compilers without well-tuned -O options generate stupid code. And (obviously) it does matter, perhaps in more cases now than it used to.


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yelang
yelang
ye lang
Mon, Jan. 19th, 2009 09:26 am (UTC)

:O

That's a new one. This is a sentiment I've never before seen expressed. In my world they matter very much.

It's a bit like saying #pragmas don't matter.



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deskitty
deskitty
Des
Mon, Jan. 19th, 2009 07:52 pm (UTC)

Well, I'm talking about it specifically in the context of desktop systems. Obviously in CPU-intensive workloads (in server or embedded systems) it makes a difference, but the argument goes that common tasks like editing Word documents, browsing the 'net, etc. are mostly I/O bound.

Clearly, that's not really the case anymore.


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