Date: Sat, 20 Mar 2010 04:46:21 +1100 (EST) From: Bruce Evans <brde@optusnet.com.au> To: John Baldwin <jhb@FreeBSD.org> Cc: src-committers@FreeBSD.org, svn-src-all@FreeBSD.org, Xin LI <delphij@FreeBSD.org>, Ivan Voras <ivoras@FreeBSD.org>, svn-src-head@FreeBSD.org, Garrett Cooper <yanefbsd@gmail.com> Subject: Re: I486_CPU and I586_CPU removed from GENERIC kernel [was Re: svn commit: r205307 - head/sys/i386/conf] Message-ID: <20100320043345.J2151@besplex.bde.org> In-Reply-To: <201003191316.04620.jhb@freebsd.org> References: <7d6fde3d1003182333m336d52fbh987035a21568250d@mail.gmail.com> <9bbcef731003190913k4f3afbd8mb4e767c40433be8e@mail.gmail.com> <201003191316.04620.jhb@freebsd.org>
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On Fri, 19 Mar 2010, John Baldwin wrote: > On Friday 19 March 2010 12:13:00 pm Ivan Voras wrote: >> SSE in the userland you mean? Regardless, I don't think there is now >> reason for compiling everything as for i386. E.g. why not add at least >> -mtune=generic or even also -march=i686 to default gcc options? >> >> http://gcc.gnu.org/onlinedocs/gcc/i386-and-x86_002d64-Options.html > > I actually suggested using -mtune=i686 several years ago for i386. Using > -mtune=generic probably would be a good thing to use when CPUTYPE is not > specified for i386 and amd64 now. Er, isn't -mtune=generic the default in gcc-4.2? I once fought with gcc-4.2 to produce kernels with similar size and compile time to ones produced by gcc-3 (impossible for the runtime since gcc got another 40% slower and kernel source size and complications expanded another 40% even when the object size didn't bloat much). It took -i386 and a couple of other flags like -fno-inline-functions-called-once (the latter is also needed to unbreak debugging with ddb and profiling). The flags had very little difference on runtime efficiency, partly because I ran the kernels mainly on Athlons which run old i386-optimized code amazingly well but gain on benefits from i686 optimizations. Optimizing Athlon kernels for Athlons also makes little difference but I usually do it. Bruce
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