Messages in this thread | | | From | "H. Peter Anvin" <> | Subject | Re: Patch to reorder functions in the vmlinux to a defined order | Date | Tue, 7 Mar 2006 15:36:00 -0800 (PST) |
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Followup to: <43FF48F2.70508@keyaccess.nl> By author: Rene Herman <rene.herman@keyaccess.nl> In newsgroup: linux.dev.kernel > > Linus Torvalds wrote: > > > The real issue is the _physical_ address. Nothing else matters. > > > > If the TLB splitting on the fixed MTRRs is an issue, it depends entirely > > on what physical address the kernel resides in, and the virtual address is > > totally inconsequential. > > > > So playing games with virtual mapping has absolutely no upsides, and it > > definitely has downsides. > > The notion was that having a fixed virtual mapping of the kernel would > allow it to be loaded anywhere physically without needing to do actual > address fixups. The bootloader could then for example at runtime decide > to load the kernel at 16MB if the machine had enough memory available, > to free up ZONE_DMA. Or not do that if running on a <= 16MB machine. >
The only machines on which ZONE_DMA matters (machines with ISA DMA devices) are also the ones which are likely to be <= 16 MB.
Yes, there are floppies, but I think having over 3 MB available for floppy DMA is plenty, and floppies are FINALLY going away...
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