Re: [Lhms-devel] Re: [PATCH 2.6.12-rc3 1/8] mm: manual page migration-rc2 -- xfs-extended-attributes-rc2.patch

["Martin J. Bligh" <mbligh@mbligh.org>]

--Christoph Lameter <christoph@lameter.com> wrote (on Tuesday, May 24, 2005 13:59:30 -0700):

> On Mon, 23 May 2005, Ray Bryant wrote:
> 
>> We need to take a different migration action based on which case we
>> are in:
>> 
>> (1)  Migrate all of the pages.
>> (2)  Migrate the non-shared pages.
>> (3)  Migrate none of the pages.
>> 
>> So we need some external way for the kernel to be told which kind of
>> mapped file this is.  That is why we need some kind of interface for
>> the user (or admininistrator) to tell us how to classify each shared
>> mapped file.
> 
> Sorry I am a bit late to the party and I know you must have said this
> before but what is the reason again not to use the page reference count to 
> determine if a page is shared? Maybe its possible to live with some 
> restrictions that the use of the page reference count brings.
> 
> Seems that touching a filesystem and the ELF headers is way off from the 
> vm.

I forget the context of this conversation, but in general if you want to
find out if the page is shared, you want mapcount, not the reference
count. Is so much easier now that we have that field ...

M.
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