Messages in this thread | | | Date | Mon, 21 Sep 2009 16:22:19 +0100 | From | Mel Gorman <> | Subject | Re: a patch drop request in -mm |
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On Tue, Sep 22, 2009 at 12:00:51AM +0900, KOSAKI Motohiro wrote: > Mel, > > Today, my test found following patch makes false-positive warning. > because, truncate can free the pages > although the pages are mlock()ed. > > So, I think following patch should be dropped. > .. or, do you think truncate should clear PG_mlock before free the page? >
Is there a reason that truncate cannot clear PG_mlock before freeing the page?
> Can I ask your patch intention?
Locked pages being freed to the page allocator were considered unexpected and a counter was in place to determine how often that situation occurred. However, I considered it unlikely that the counter would be noticed so the warning was put in place to catch what class of pages were getting freed locked inappropriately. I think a few anomolies have been cleared up since. Ultimately, it should have been safe to delete the check.
> > > ============================================================= > commit 7a06930af46eb39351cbcdc1ab98701259f9a72c > Author: Mel Gorman <mel@csn.ul.ie> > Date: Tue Aug 25 00:43:07 2009 +0200 > > When a page is freed with the PG_mlocked set, it is considered an > unexpected but recoverable situation. A counter records how often this > event happens but it is easy to miss that this event has occured at > all. This patch warns once when PG_mlocked is set to prompt debuggers > to check the counter to see how often it is happening. > > Signed-off-by: Mel Gorman <mel@csn.ul.ie> > Reviewed-by: Christoph Lameter <cl@linux-foundation.org> > Acked-by: Johannes Weiner <hannes@cmpxchg.org> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 28c2f3e..251fd73 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -494,6 +494,11 @@ static inline void __free_one_page(struct page *page, > */ > static inline void free_page_mlock(struct page *page) > { > + WARN_ONCE(1, KERN_WARNING > + "Page flag mlocked set for process %s at pfn:%05lx\n" > + "page:%p flags:%#lx\n", > + current->comm, page_to_pfn(page), > + page, page->flags|__PG_MLOCKED); > __dec_zone_page_state(page, NR_MLOCK); > __count_vm_event(UNEVICTABLE_MLOCKFREED); > } >
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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