From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 916CC6008E4 for ; Tue, 3 Aug 2010 00:31:53 -0400 (EDT) Date: Tue, 3 Aug 2010 13:31:09 +0900 From: Daisuke Nishimura Subject: Re: [PATCH -mm 1/5] quick lookup memcg by ID Message-Id: <20100803133109.c0e6f150.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20100802191304.8e520808.kamezawa.hiroyu@jp.fujitsu.com> References: <20100802191113.05c982e4.kamezawa.hiroyu@jp.fujitsu.com> <20100802191304.8e520808.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: linux-mm@kvack.org, "balbir@linux.vnet.ibm.com" , vgoyal@redhat.com, m-ikeda@ds.jp.nec.com, gthelen@google.com, "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" , Daisuke Nishimura List-ID: Hi. Thank you for all of your works. Several comments are inlined. On Mon, 2 Aug 2010 19:13:04 +0900 KAMEZAWA Hiroyuki wrote: > From: KAMEZAWA Hiroyuki > > Now, memory cgroup has an ID per cgroup and make use of it at > - hierarchy walk, > - swap recording. > > This patch is for making more use of it. The final purpose is > to replace page_cgroup->mem_cgroup's pointer to an unsigned short. > > This patch caches a pointer of memcg in an array. By this, we > don't have to call css_lookup() which requires radix-hash walk. > This saves some amount of memory footprint at lookup memcg via id. > > Changelog: 20100730 > - fixed rcu_read_unlock() placement. > > Signed-off-by: KAMEZAWA Hiroyuki > --- > init/Kconfig | 11 +++++++++++ > mm/memcontrol.c | 48 ++++++++++++++++++++++++++++++++++-------------- > 2 files changed, 45 insertions(+), 14 deletions(-) > > Index: mmotm-0727/mm/memcontrol.c > =================================================================== > --- mmotm-0727.orig/mm/memcontrol.c > +++ mmotm-0727/mm/memcontrol.c > @@ -292,6 +292,30 @@ static bool move_file(void) > &mc.to->move_charge_at_immigrate); > } > > +/* 0 is unused */ > +static atomic_t mem_cgroup_num; > +#define NR_MEMCG_GROUPS (CONFIG_MEM_CGROUP_MAX_GROUPS + 1) > +static struct mem_cgroup *mem_cgroups[NR_MEMCG_GROUPS] __read_mostly; > + > +static struct mem_cgroup *id_to_memcg(unsigned short id) > +{ > + /* > + * This array is set to NULL when mem_cgroup is freed. > + * IOW, there are no more references && rcu_synchronized(). > + * This lookup-caching is safe. > + */ > + if (unlikely(!mem_cgroups[id])) { > + struct cgroup_subsys_state *css; > + > + rcu_read_lock(); > + css = css_lookup(&mem_cgroup_subsys, id); > + rcu_read_unlock(); > + if (!css) > + return NULL; > + mem_cgroups[id] = container_of(css, struct mem_cgroup, css); > + } > + return mem_cgroups[id]; > +} id_to_memcg() seems to be called under rcu_read_lock() already, so I think rcu_read_lock()/unlock() would be unnecessary. > Index: mmotm-0727/init/Kconfig > =================================================================== > --- mmotm-0727.orig/init/Kconfig > +++ mmotm-0727/init/Kconfig > @@ -594,6 +594,17 @@ config CGROUP_MEM_RES_CTLR_SWAP > Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page > size is 4096bytes, 512k per 1Gbytes of swap. > > +config MEM_CGROUP_MAX_GROUPS > + int "Maximum number of memory cgroups on a system" > + range 1 65535 > + default 8192 if 64BIT > + default 2048 if 32BIT > + help > + Memory cgroup has limitation of the number of groups created. > + Please select your favorite value. The more you allow, the more > + memory will be consumed. This consumes vmalloc() area, so, > + this should be small on 32bit arch. > + We don't use vmalloc() area in this version :) Thanks, Daisuke Nishimura. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org