Messages in this thread | | | Date | Tue, 02 Jun 2015 11:33:05 +0200 | From | Vlastimil Babka <> | Subject | Re: [PATCH] hugetlb: Do not account hugetlb pages as NR_FILE_PAGES |
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On 06/02/2015 11:25 AM, Michal Hocko wrote: > On Mon 25-05-15 17:24:28, Vlastimil Babka wrote: >> On 05/22/2015 04:35 PM, Mel Gorman wrote: >>>> >>>> Thanks! >>>> >>>>> This makes a lot of sense to me. The only thing I worry about is the >>>>> proliferation of PageHuge(), a function call, in relatively hot paths. >>>> >>>> I've tried that (see the patch below) but it enlarged the code by almost >>>> 1k >>>> text data bss dec hex filename >>>> 510323 74273 44440 629036 9992c mm/built-in.o.before >>>> 511248 74273 44440 629961 99cc9 mm/built-in.o.after >>>> >>>> I am not sure the code size increase is worth it. Maybe we can reduce >>>> the check to only PageCompound(page) as huge pages are no in the page >>>> cache (yet). >>>> >>> >>> That would be a more sensible route because it also avoids exposing the >>> hugetlbfs destructor unnecessarily. >> >> You could maybe do test such as (PageCompound(page) && PageHuge(page)) to >> short-circuit the call while remaining future-proof. > > How about this?
Yeah (see below)
> --- > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 91b7f9b2b774..bb8a70e8fc77 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -547,7 +547,13 @@ static inline void ClearPageCompound(struct page *page) > #endif /* !PAGEFLAGS_EXTENDED */ > > #ifdef CONFIG_HUGETLB_PAGE > -int PageHuge(struct page *page); > +int __PageHuge(struct page *page); > +static inline int PageHuge(struct page *page) > +{ > + if (!PageCompound(page))
Perhaps the above as likely()?
[...]
> -EXPORT_SYMBOL_GPL(PageHuge); > +EXPORT_SYMBOL_GPL(__PageHuge); > > /* > * PageHeadHuge() only returns true for hugetlbfs head page, but not for >
Do the same thing here by inlining the PageHead() test? I guess the page_to_pgoff and __compound_tail_refcounted callers are rather hot?
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