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SubjectRe: [patch] jiffies wraparound [Re: 2.1.125 Show stopper list: Draft]


On Tue, 27 Oct 1998, MOLNAR Ingo wrote:
>
> On Tue, 27 Oct 1998, Linus Torvalds wrote:
>
> > We don't. Notice my "on architectures that need it" comment. Which
> > definitely means that i386 will never see it.
>
> never? :) i'm eyeing with the PPro 2MB page stuff, it's probably buggy and
> seems to be discontinued, but is interesting nevertheless ;)

The ppro 2M and 4M extensions aren't general-purpose enough to make it
useful to consider a "page size". Even when you enable the silly
three-level page tables, the basic page size if 4kB.

The 2M and 4M versions can be useful for specific cases (we obviously
already use the 4M pages for the kernel itself), but thinking that they
should be exported as a supported page size to user mode is just silly.

We could silently and magically use them for certain things (doing a
mmap(/dev/mem) using them for XFree86 comes to mind), but while I've often
heard the claims that TLB miss time makes a difference to graphics work, I
don't actually believe it for a second.

Linus


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