From f1e61557f0230d51a3df8d825f2c156e75563bff Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Fri, 6 Nov 2015 16:29:50 -0800 Subject: mm: pack compound_dtor and compound_order into one word in struct page The patch halves space occupied by compound_dtor and compound_order in struct page. For compound_order, it's trivial long -> short conversion. For get_compound_page_dtor(), we now use hardcoded table for destructor lookup and store its index in the struct page instead of direct pointer to destructor. It shouldn't be a big trouble to maintain the table: we have only two destructor and NULL currently. This patch free up one word in tail pages for reuse. This is preparation for the next patch. Signed-off-by: Kirill A. Shutemov Reviewed-by: Michal Hocko Acked-by: Vlastimil Babka Reviewed-by: Andrea Arcangeli Cc: "Paul E. McKenney" Cc: Andi Kleen Cc: Aneesh Kumar K.V Cc: Christoph Lameter Cc: David Rientjes Cc: Hugh Dickins Cc: Joonsoo Kim Cc: Sergey Senozhatsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b8d560afe266..fae1bd6f9f37 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -229,6 +229,15 @@ static char * const zone_names[MAX_NR_ZONES] = { #endif }; +static void free_compound_page(struct page *page); +compound_page_dtor * const compound_page_dtors[] = { + NULL, + free_compound_page, +#ifdef CONFIG_HUGETLB_PAGE + free_huge_page, +#endif +}; + int min_free_kbytes = 1024; int user_min_free_kbytes = -1; @@ -458,7 +467,7 @@ void prep_compound_page(struct page *page, unsigned long order) int i; int nr_pages = 1 << order; - set_compound_page_dtor(page, free_compound_page); + set_compound_page_dtor(page, COMPOUND_PAGE_DTOR); set_compound_order(page, order); __SetPageHead(page); for (i = 1; i < nr_pages; i++) { -- cgit v1.2.3