Re: Fairness in love and swapping

[Rik van Riel <H.H.vanRiel@fys.ruu.nl>]

On Thu, 26 Feb 1998, Stephen C. Tweedie wrote:

> > Without my mmap-age patch, page cache pages aren't aged
> > at all... They're just freed whenever they weren't referenced
> > since the last scan. The PAGE_AGE_VALUE is quite useless IMO
> > (but I could be wrong, Stephen?).
> 
> They _are_ useful for mapped images such as binaries (which are swapped
> out by vmscan.c, not filemap.c), but not for otherwise unused, pure
> cached pages.

AFAIK, mapped images aren't part of a proces' RSS, but
are page-cached (page->inode type of RSS). And swapping
of those vma's _is_ done in shrink_mmap() in filemap.c.

Furthermore, it's quite useful if your read-ahead pages
stay in memory for a while so you don't read them two
or even three times before they're actually used.

But if I've overlooked something, I'd really like to
hear about it... A bit of a clue never hurts when
coding up new patches :-)

Rik.
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