Date: Tue, 29 Apr 2003 19:54:06 +0200 From: Charlie Clark <charlie@begeistert.org> To: freebsd-newbies@freebsd.org Subject: Re: kernel optimized for Athlon XP 1800+ Message-ID: <20030429195406.3583.17@wonderland.1051603270.fake> In-Reply-To: <200304291029.49957.DavidJohnson@Siemens.com> References: <20030429063543.GA888@home.arachne.cz> <200304291029.49957.DavidJohnson@Siemens.com>
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On 2003-04-29 at 19:29:49 [+0200], Johnson David wrote: > Those CPU settings for the kernel are not for optimization. They're for > accessing functionality. If you run dmesg and look near the top, you'll > find that FreeBSD kernel is detecting your CPU as a "686-class CPU" > regardless. The kernel is not optimized because it's just too close to > the metal. Optimize it too much and it will break every time gcc changes > its optimizer ever so slightly. I'm just curious as to why someone would be so keen to optimise the kernel: the discussion seemed to be aimed at squeezing the last quantum of performance out of a specific processor. This isn't ever likely to be possible for a system that can run on different processors like FreeBSD at least my understanding is that portability comes at the cost of performance. The best way to optimise is to remove things you don't need then hand tweak the code, use a compiler that's optimised for the processor, ie. Intel rather than gcc and enable all the switches. But as was said - there is a separate mailing list for this. Charlie
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