Messages in this thread | | | Date | Tue, 4 Feb 2014 10:53:32 +0900 | From | Joonsoo Kim <> | Subject | Re: [patch] mm, compaction: avoid isolating pinned pages fix |
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On Mon, Feb 03, 2014 at 05:20:46PM -0800, David Rientjes wrote: > On Tue, 4 Feb 2014, Joonsoo Kim wrote: > > > I think that you need more code to skip this type of page correctly. > > Without page_mapped() check, this code makes migratable pages be skipped, > > since if page_mapped() case, page_count() may be more than zero. > > > > So I think that you need following change. > > > > (!page_mapping(page) && !page_mapped(page) && page_count(page)) > > > > These pages returned by get_user_pages() will have a mapcount of 1 so this > wouldn't actually fix the massive lock contention. page_mapping() is only > going to be NULL for pages off the lru like these are for > PAGE_MAPPING_ANON.
Okay. It can't fix your situation. Anyway, *normal* anon pages may be mapped and have positive page_count(), so your code such as '!page_mapping(page) && page_count(page)' makes compaction skip these *normal* anon pages and this is incorrect behaviour.
Thanks.
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