Messages in this thread | | | Date | Wed, 11 Mar 2020 12:25:20 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH] mm/hugetlb: remove unnecessary memory fetch in PageHeadHuge() |
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On Wed, 11 Mar 2020, Vlastimil Babka wrote:
> Commit f1e61557f023 ("mm: pack compound_dtor and compound_order into one word > in struct page") changed compound_dtor from a pointer to an array index in > order to pack it. To check if page has the hugeltbfs compound_dtor, we can > just compare the index directly without fetching the function pointer. > Said commit did that with PageHuge() and we can do the same with PageHeadHuge() > to make the code a bit smaller and faster. > > Signed-off-by: Vlastimil Babka <vbabka@suse.cz> > Cc: Mike Kravetz <mike.kravetz@oracle.com> > Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Fixes: f1e61557f023 ("mm: pack compound_dtor and compound_order into one word in struct page")
Acked-by: David Rientjes <rientjes@google.com>
[+nehaagarwal]
We've been running with this patch for a few years and it works as intended.
> --- > mm/hugetlb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index dd8737a94bec..ba1ca452aa7f 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -1313,7 +1313,7 @@ int PageHeadHuge(struct page *page_head) > if (!PageHead(page_head)) > return 0; > > - return get_compound_page_dtor(page_head) == free_huge_page; > + return page_head[1].compound_dtor == HUGETLB_PAGE_DTOR; > } > > pgoff_t __basepage_index(struct page *page)
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