Date: Wed, 24 May 2000 14:23:30 -0500 From: Dan Nelson <dnelson@emsphone.com> To: Chuck Paterson <cp@bsdi.com> Cc: arch@freebsd.org Subject: Re: Preemptive kernel on older X86 hardware Message-ID: <20000524142329.B15434@dan.emsphone.com> In-Reply-To: <200005241846.MAA07977@berserker.bsdi.com>; from "Chuck Paterson" on Wed May 24 12:46:04 GMT 2000 References: <200005241846.MAA07977@berserker.bsdi.com>
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In the last episode (May 24), Chuck Paterson said: > Dan Nelson said: > }Why not just make it conditional on the "cpu I386_CPU" line in the > }kernel Makefile? The comment already reads: > } > } deleting the specification for CPUs you don't need to use may make > } parts of the system run faster. This is especially true removing > } I386_CPU. > > Technically this works just fine. > > I personally don't understand the implications of saying that a > kernel build is necessary. I'm not saying it is bad, I just saying I > don't understand. If people say this is acceptable then this is fine. It's only necessary if an optimized SMP-aware kernel can't run on a 386 (due to use pentium-specific instructions) *and* a kernel that runs on a 386 is too slow to be usable on an SMP box (due to lack of fast pentium-specific instructions). The current FreeBSD build process requires you to do a recompile to enable SMP, so given that we need to recompile anyhow, it's not that big a deal. When we get to the point where a single kernel runs optimally on both SMP and UP hardware, then it will be an issue. BTW, FreeBSD does a little bit of per-processor runtime optimization in the kernel already; bcopy, bzero, and copyin/out get replaced with 586-specific functions when the kernel is booting, if a pentium is detected (see sys/i386/isa/npx.c). -- Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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