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    SubjectRe: How to reclaim inode pages on demand
    On Wed, 10 Aug 2005, Dave Hansen wrote:

    > On Wed, 2005-08-10 at 18:27 +0100, Mel Gorman wrote:
    > > I later linearly scan the mem_map looking for pages that can be freed up
    > > (usually LRU pages). I was expecting any page with PG_inode set to have a
    > > page->mapping but not all of them do. It is the pages without a ->mapping
    > > that are confusing the hell out of me.
    > How about putting a check for PG_inode and a periodic dump_stack()
    > wherever page->mapping is cleared? That should at least let you catch
    > the culprit who is clearing them. __remove_from_page_cache() is the only
    > real place I see this being done.

    Will do, it might shed some light on whats happening.

    > Are you remembering to clean PG_inode when a page is freed?

    Yes, I was using the allocator to count how many inode-related pages there
    were in the system. The answer was lots, another reason why I'm thinking
    that I picked the worst possible benchmark to test this stuff with.

    > Perhaps
    > it's allocated for the page cache, reclaimed, returned to the allocator,
    > and reallocated as anonymous memory where you're seeing the null
    > ->mapping. Might want to check for PG_inode in free_pages_check().

    I am 99.99% certain I make that check but I can't double check the code
    until late in the weekend.

    Mel Gorman
    Part-time Phd Student Java Applications Developer
    University of Limerick IBM Dublin Software Lab
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