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SubjectRe: Subtle MM bug
Andrea Arcangeli <> writes:

> On Wed, Jan 10, 2001 at 11:46:03AM +0000, David Woodhouse wrote:
> > So the VM code spends a fair amount of time scanning lists of pages which
> > it really can't do anything about?
> Yes.
> > Would it be possible to put such pages on different list, so that the VM
> Currently to unmap the other pages we have to waste time on those unfreeable
> pages as well.
> Once I or other developer finishes with the reverse lookup from page to
> pte-chain (an implementation from DaveM just exists) we'll be able to put them
> in a separate lru, but it's certainly not a 2.4.1-pre2 thing.

Why do we even want to do reverse page tables?
It seems everyone is assuming this is a good thing and except for being
a touch more flexible I don't see what this buys us (besides more locked memory).

My impression with the MM stuff is that everyone except linux is
trying hard to clone BSD instead of thinking through the issues

And because of the extra overhead this doesn't look to be a win on a
heavily loaded box with no swap. And probably only glibc mmaped.

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