Date: Tue, 02 Jul 2002 17:12:50 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: current@FreeBSD.ORG Cc: Matthew Dillon <dillon@apollo.backplane.com> Subject: Re: -current results (was something funny with soft updates?) Message-ID: <3D224182.BFE8CF22@mindspring.com> References: <Pine.BSF.4.21.0206281233500.75410-100000@InterJet.elischer.org> <200207020314.g623Eke5038019@apollo.backplane.com> <20020702164756.E70767@dragon.nuxi.com>
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David O'Brien wrote: > On Mon, Jul 01, 2002 at 08:14:46PM -0700, Matthew Dillon wrote: > > My conclusion is that softupdates is working fine and (A) the new GCC > > is a whole lot less efficient then the old GCC > > You really cannot say this -- GCC 3.1 does things 2.95 doesn't. 3.1 has > a totally rewritten code scheduler. People can't get Pentium-4 and > Athlon tbird specific optimizations for free. > > You almost seem to be making a claim on the quality of generated code, > vs. just the run-time of the compiler. The two are different. But it's possible to be conclusive. The way you would do this is to compile the 3.1 compiler with the 3.1 compiler for one test, and compile the 3.1 compiler with the 2.95 compiler for the other. If the 3.1 compiler compiled with the 2.95 compiler is faster, then 2.95 "wins" on code generation. I rather suspect that 3.1 is doing additional work, other than "intentionally" bloating the boot blocks into unusability, etc., and you will find that the 3.1 compiled 3.1 is more efficient than the 2.95 compiled 3.1. At which point it becomes a trade between compilation time vs. run time efficiency. Personally, I prefer knowing my code should work before giving it to the compiler, rather than using the compiler to think about things I'm too lazy/incapable of thinking of on my own. Given that, I would always favor a trade for faster run time and slower compile time. I think maybe the main problem here is that people have been utilizing the wall time of "make world" as some kind of generic benchmark for so long that the idea of any increase in the wall time can't help but trigger a gut reaction against it. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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