Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757772Ab2BNHXN (ORCPT ); Tue, 14 Feb 2012 02:23:13 -0500 Received: from mail-vx0-f174.google.com ([209.85.220.174]:60931 "EHLO mail-vx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755100Ab2BNHXK convert rfc822-to-8bit (ORCPT ); Tue, 14 Feb 2012 02:23:10 -0500 MIME-Version: 1.0 In-Reply-To: <20120214121631.782352f2.kamezawa.hiroyu@jp.fujitsu.com> References: <20120214120414.025625c2.kamezawa.hiroyu@jp.fujitsu.com> <20120214121631.782352f2.kamezawa.hiroyu@jp.fujitsu.com> From: Greg Thelen Date: Mon, 13 Feb 2012 23:22:50 -0800 Message-ID: Subject: Re: [PATCH 6/6 v4] memcg: fix performance of mem_cgroup_begin_update_page_stat() To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "hannes@cmpxchg.org" , Michal Hocko , "akpm@linux-foundation.org" , Ying Han , Hugh Dickins Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2265 Lines: 61 On Mon, Feb 13, 2012 at 7:16 PM, KAMEZAWA Hiroyuki wrote: > From 3377fd7b6e23a5d2a368c078eae27e2b49c4f4aa Mon Sep 17 00:00:00 2001 > From: KAMEZAWA Hiroyuki > 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 "a memcg is moving or not". s/a memcg/any memcg/ > By this, the caller doesn't need to visit page_cgroup and memcg. s/By/With/ > 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(). Out of curiosity, what is the performance of the mmap program before this series? > 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. > > Signed-off-by: KAMEZAWA Hiroyuki Acked-by: Greg Thelen -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/