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Message-ID: <Pine.LNX.4.64.0711061856400.5565@schroedinger.engr.sgi.com>
Date: Tue, 6 Nov 2007 19:02:47 -0800 (PST)
From: Christoph Lameter <clameter@....com>
To: Rik van Riel <riel@...hat.com>
cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH 3/10] define page_file_cache
On Tue, 6 Nov 2007, Rik van Riel wrote:
> > I think we could add a flag to the bdi to indicate wheter the backing
> > store is a disk file. In fact you can also deduce if if a device has
> > no writeback capability set in the BDI.
> >
> > > Unfortunately this needs to use a page flag, since the
> > > PG_swapbacked state needs to be preserved all the way
> > > to the point where the page is last removed from the
> > > LRU. Trying to derive the status from other info in
> > > the page resulted in wrong VM statistics in earlier
> > > split VM patchsets.
> >
> > The bdi may avoid that extra flag.
>
> The bdi will no longer be accessible by the time a page
> makes it to free_hot_cold_page, which is one place in the
> kernel where this information is needed.
At that point you need only information about which list the page
was put on. Dont we need something like PageLRU -> PageFileLRU
and PageMemLRU?
The page may change its nature I think? What if a page becomes
swap backed?
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