Re: [PATCH] Reclaim orphaned swap pages

[Marcelo Tosatti <marcelo@conectiva.com.br>]

On Tue, 3 Apr 2001, Richard Jerrell wrote:

> > > That's not really what I'm getting at.  Currently if you run a memory
> > > intensive application, quit after it's pages are on an lru, and try to
> > > restart, you won't be able to get the memory.  This is because pages which
> > > are sitting around in the swap cache are not counted as free, and they
> > > should be, because they are freeable.
> > 
> > No. Dirty swapcache pages which have pte's referencing them are not
> > freeable.
> 
> If you quit the application, it no longer has ptes which are referencing
> the page.  If, in addition, this page no longer has any ptes referencing
> it, then it is wasting space.  That is why we free the page (providing
> that the swap entry is not shared either).  Otherwise, you will run out of
> memory because everything is stuck in the swap cache until it gets
> laundered, regardless of whether anyone is still referencing the
> page.  That is not a good thing, which is what the patch fixes.

Right.

But you should not count _all_ swapcache pages as freeable. 



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