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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