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Date: Sun, 4 Nov 2001 19:10:14 -0800
From: Mike Fedyk <mfedyk@matchmail.com>
To: Ed Tomlinson <tomlins@cam.org>
Cc: Rik van Riel <riel@conectiva.com.br>, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH] vm_swap_full
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On Sun, Nov 04, 2001 at 09:58:17PM -0500, Ed Tomlinson wrote:
> On November 4, 2001 09:08 pm, Mike Fedyk wrote:
> > On Sun, Nov 04, 2001 at 02:36:34PM -0200, Rik van Riel wrote:
> > > On Sun, 4 Nov 2001, Ed Tomlinson wrote:
> > > > -/* Swap 50% full? Release swapcache more aggressively.. */
> > > > -#define vm_swap_full() (nr_swap_pages*2 < total_swap_pages)
> > > > +/* Free swap less than inactive pages? Release swapcache more
> > > > aggressively.. */ +#define vm_swap_full() (nr_swap_pages <
> > > > nr_inactive_pages)
> > > >
> > > > Comments?
> > >
> > > Makes absolutely no sense for systems which have more
> > > swap than RAM, eg. a 64MB system with 200MB of swap.
> >
> > How does the inactive list get bigger than physical ram?
> >
> > If swap is bigger than ram, there is *no* possibility of the inactive list
> > being bigger than swap, and thus no aggressive swapping...
> 
> nr_swap_pages is the number of swap pages free.  

Oh, I thought it was total swap pages...

>The idea is to start
> aggressive swap only when we are at risk of running out of swap.  This way
> we get to take full advantage of throwing away clean pages that are backed
> up by swap when under vm pressure. 
> 
Yes.  My point is that the inactive list can't get bigger than RAM, and thus
if swap is bigger than ram this case wouldn't trigger...

But now that nr_swap_pages is *free* swap, you'll have to add another test
for (swap > RAM)... 

Mike