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SubjectRe: 2.4.10 VM: what avoids from having lots of unwriteable inactive pages


On Mon, 24 Sep 2001, Linus Torvalds wrote:

>
> On Mon, 24 Sep 2001, Marcelo Tosatti wrote:
> >
> > What avoids us from having a lot of unfreeable (eg mapped by ptes) pages
> > on the inactive list ?
>
> Nothing.
>
> If we can't shrink them, we'll fall out and do vmscanning.
>
> Which is exactly what we want to do - it automatically acts as a "uhhuh,
> we've got to do something now" thing.

Think about a case where the inactive list if _full_ of mapped pages.
(which can easily happen, because one fault (do_swap_page) will _not_ move
the page to the active list directly --- it has to be accessed (Referenced
bit) twice (mark_page_accessed)).

We _think_ we don't have a shortage, so we won't call refill_inactive().

We keep calling swap_out(), which will not deactivate pages which _can_ be
written out, until we deactivate the pte's from the pages which are on the
inactive list.

Nothing prevents that, right ?

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