Commit 0753b0ef authored Jan 07, 2009 by Fernando Luis Vazquez Cao Committed by Linus Torvalds Jan 08, 2009

memcg: do not recalculate section unnecessarily in init_section_page_cgroup

In init_section_page_cgroup() the section a given pfn belongs to is
calculated at the top of the function and, despite the fact that the
pfn/section correspondence does not change, it is recalculated further
down the same function. By computing this just once and reusing that
value we save some bytes in the object file and do not waste CPU cycles.

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 01b1ae63

mm/page_cgroup.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -103,13 +103,11 @@ struct page_cgroup lookup_page_cgroup(struct page page)
		/* __alloc_bootmem...() is protected by !slab_available() */
		static int __init_refok init_section_page_cgroup(unsigned long pfn)
		{
		struct mem_section *section;
		struct mem_section *section = __pfn_to_section(pfn);
		struct page_cgroup base, pc;
		unsigned long table_size;
		int nid, index;

		section = __pfn_to_section(pfn);

		if (!section->page_cgroup) {
		nid = page_to_nid(pfn_to_page(pfn));
		table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
		@@ -145,7 +143,6 @@ static int __init_refok init_section_page_cgroup(unsigned long pfn)
		__init_page_cgroup(pc, pfn + index);
		}

		section = __pfn_to_section(pfn);
		section->page_cgroup = base - pfn;
		total_usage += table_size;
		return 0;