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SubjectRe: [PATCH] mm: Warn once when a page is freed with PG_mlocked set (resend)
On Wed, Jul 15, 2009 at 02:45:09PM +0200, Johannes Weiner wrote:
> Hello Mel,
>
> On Wed, Jul 15, 2009 at 11:48:34AM +0100, Mel Gorman wrote:
> > 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>
> > ---
> > mm/page_alloc.c | 16 ++++++++++++----
> > 1 file changed, 12 insertions(+), 4 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index caa9268..f8902e7 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -495,8 +495,16 @@ static inline void free_page_mlock(struct page *page)
> > static void free_page_mlock(struct page *page) { }
> > #endif
> >
> > -static inline int free_pages_check(struct page *page)
> > -{
> > +static inline int free_pages_check(struct page *page, int wasMlocked)
> > +{
> > + if (unlikely(wasMlocked)) {
> > + WARN_ONCE(1, KERN_WARNING
> > + "Page flag mlocked set for process %s at pfn:%05lx\n"
> > + "page:%p flags:0x%lX\n",
> > + current->comm, page_to_pfn(page),
> > + page, page->flags|__PG_MLOCKED);
>
> Since the warning is the only action in this branch, wouldn't
> WARN_ONCE(wasMlocked, KERN_WARNING ...) be better?
>

It was to have the unlikely() but now that I look at WARN_ONCE(), it
looks like it does the unlikely() part already. Will send another
version. Thanks

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab


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