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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>
This commit is contained in:
Fernando Luis Vazquez Cao 2009-01-07 18:07:51 -08:00 committed by Linus Torvalds
parent 01b1ae63c2
commit 0753b0ef3b
1 changed files with 1 additions and 4 deletions
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5
mm/page_cgroup.c
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@ -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;