Re: grow_dev_page's __GFP_MOVABLE

[Badari Pulavarty <pbadari@gmail.com>]

On Fri, 2008-03-14 at 11:47 +0000, Mel Gorman wrote:
> On (13/03/08 16:50), Badari Pulavarty didst pronounce:
> > > > <SNIP>
> > > > page_owner shows:
> > > > 
> > > > Page allocated via order 0, mask 0x120050
> > > > PFN 30625 Block 7 type 2          Flags      L
> > > 
> > > This page is indicated as being on the LRU so it should have been possible
> > > to reclaim. Is memory hot-remove making any effort to reclaim this page or
> > > is it depending only on page migration?
> > 
> > offline_pages() finds all the pages on LRU and tries to migrate them by
> > calling unmap_and_move(). I don't see any explicit attempt to reclaim.
> > It tries to migrate the page (move_to_new_page()), but what I have seen
> > in the past is that these pages have buffer heads attached to them. 
> > So, migrate_page_move_mapping() fails to release the page. (BTW,
> > I narrowed this in Oct 2007 and forgot most of the details). I can
> > take a closer look again. Can we reclaim these pages easily ?
> > 
> 
> They should be, or huge page allocations using lumpy reclaim would also
> be failing all the time.

Hi Mel,

These pages are on LRU and clean. In order to reclaim these pages
(looking at pageout()), all we need to do is try_to_release_page().
fallback_migrate_page() does this but fails to free it up. What
else I can do here to force reclaim these ?

Thanks,
Badari

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