Date: Wed, 07 May 2008 10:22:45 -0500 From: Nathan Whitehorn <nathanw@uchicago.edu> To: grehan@freebsd.org Cc: freebsd-ppc@freebsd.org Subject: Re: UMA_MD_SMALL_ALLOC Message-ID: <4821C945.5030008@uchicago.edu> In-Reply-To: <4821C85A.7090605@freebsd.org> References: <4821C6AB.3080101@uchicago.edu> <4821C85A.7090605@freebsd.org>
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Peter Grehan wrote: > Hi Nathan, > >> In doing the G5 port, I have a problem with the UMA_MD_SMALL_ALLOC >> option. Because the G5 does not have BAT, this is broken. Even if we >> were to emulate it with pages, this is not a useful thing to have, >> since the point of the option would be defeated. But removing it would >> pessimize the G3/G4 port (the AIM code also panics late in boot >> without it, but that is a separate issue). >> >> There doesn't seem to be a way to twiddle it at runtime, which is a >> major problem if we want to have a single kernel running on all OEA >> machines. So I'm not sure what to do. Thoughts? > > A long time ago I talked to Alan Cox about modifying this option so it > could be done at run-time, and he seemed agreeable. The mips port has a > similar issue in that only the lower 512MB of RAM is direct-mapped, so a > run-time decision would help them too (though it would be based on free > pages and not processor variant). Oh, great. That would be really convenient. >> Also, an update on the G5 port: the PMAP stuff is done to the point >> where the kernel boots all the way to panicing about not having a PIC, >> which is late in the boot process and implies that only device support >> remains. Trap handling is up and running as well. And (with the >> exception of UMA_MD_SMALL_ALLOC) the same kernel also boots on my G3. > > Fantastic ! Post some patches, I'll give it a try. > > Have you changed the sync_icache code to dynamically switch to 128 > bytes for the G5 ? Yep. I'll post some patches later, once I've cleaned them up a little (they are a bit littered with printf(), /* code */ and #if 0 at the moment). -Nathan
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