Re: Best way to extend try_to_free_pages()?

["Stephen C. Tweedie" <sct@redhat.com>]

Hi,

On Tue, May 16, 2000 at 09:51:17PM -0400, frankeh@us.ibm.com wrote:

> I assume everything could register as a first class citizen, including file
> cache, etc.....
> Some thoughts along the line.
> Would it make sense to priorities such <kernel-memory-clients>.
> Wouldn't it make sense to specify the number of pages as part of the
> interface?
> Do you assume fairness among memory clients based on the cyclic queue if
> priorities is not desirable.

Chris Mason and I have already been looking at doing something
similar, but on a per-page basis, to allow advanced filesystems to
release memory in a controlled manner.  This is particularly
necessary for journaled filesystems, in which releasing certain 
data may require a transaction commit --- until the commit, there
is just no way shrink_mmap() will be able to free those pages, so
there has to be a way for shrink_mmap() to let the filesystem know
that it wants some memory back.

The route we'll probably go for this is through address_space_operations
callbacks from shrink_mmap.  That allows proper fairness --- all fses
can share the same lru that way.

--Stephen
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