Re: [PATCH -mm 14/24] Ramfs and Ram Disk pages are unevictable

From: Rik van Riel
Date: Thu Jun 12 2008 - 13:30:37 EST


On Thu, 12 Jun 2008 10:54:18 +1000
Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:
> On Thursday 12 June 2008 04:42, Rik van Riel wrote:
> > From: Lee Schermerhorn <Lee.Schermerhorn@xxxxxx>
> >
> > Christoph Lameter pointed out that ram disk pages also clutter the
> > LRU lists. When vmscan finds them dirty and tries to clean them,
> > the ram disk writeback function just redirties the page so that it
> > goes back onto the active list. Round and round she goes...

> This isn't the case for brd any longer. It doesn't use the buffer
> cache as its backing store, so the buffer cache is reclaimable.

What does that mean?

I know that pages of files that got paged into the page
cache from the ramdisk can be evicted (back to the ram
disk), but how do the brd pages themselves behave?

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