On Fri, Feb 17, 2012 at 06:28:51PM +0900, KAMEZAWA Hiroyuki wrote: > >From 07d3ce332ee4bc1eaef4b8fb2019b0c06bd7afb1 Mon Sep 17 00:00:00 2001 > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Date: Mon, 6 Feb 2012 12:14:47 +0900 > Subject: [PATCH 6/6] memcg: fix performance of mem_cgroup_begin_update_page_stat() > > mem_cgroup_begin_update_page_stat() should be very fast because > it's called very frequently. Now, it needs to look up page_cgroup > and its memcg....this is slow. > > This patch adds a global variable to check "any memcg is moving or not". > With this, the caller doesn't need to visit page_cgroup and memcg. > > Here is a test result. A test program makes page faults onto a file, > MAP_SHARED and makes each page's page_mapcount(page) > 1, and free > the range by madvise() and page fault again. This program causes > 26214400 times of page fault onto a file(size was 1G.) and shows > shows the cost of mem_cgroup_begin_update_page_stat(). > > Before this patch for mem_cgroup_begin_update_page_stat() > [kamezawa@bluextal test]$ time ./mmap 1G > > real 0m21.765s > user 0m5.999s > sys 0m15.434s > > 27.46% mmap mmap [.] reader > 21.15% mmap [kernel.kallsyms] [k] page_fault > 9.17% mmap [kernel.kallsyms] [k] filemap_fault > 2.96% mmap [kernel.kallsyms] [k] __do_fault > 2.83% mmap [kernel.kallsyms] [k] __mem_cgroup_begin_update_page_stat > > After this patch > [root@bluextal test]# time ./mmap 1G > > real 0m21.373s > user 0m6.113s > sys 0m15.016s > > In usual path, calls to __mem_cgroup_begin_update_page_stat() goes away. > > Note: we may be able to remove this optimization in future if > we can get pointer to memcg directly from struct page. > > Acked-by: Greg Thelen <gthelen@xxxxxxxxxx> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>