Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760060Ab0HEKCQ (ORCPT ); Thu, 5 Aug 2010 06:02:16 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:33134 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754727Ab0HEKCM (ORCPT ); Thu, 5 Aug 2010 06:02:12 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Thu, 5 Aug 2010 18:57:13 +0900 From: KAMEZAWA Hiroyuki To: KAMEZAWA Hiroyuki Cc: linux-mm@kvack.org, "balbir@linux.vnet.ibm.com" , "nishimura@mxp.nes.nec.co.jp" , vgoyal@redhat.com, m-ikeda@ds.jp.nec.com, gthelen@google.com, "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" Subject: [PATCH 1/4 -mm][memcg] quick ID lookup in memcg Message-Id: <20100805185713.4d09339e.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20100805184434.3a29c0f9.kamezawa.hiroyu@jp.fujitsu.com> References: <20100805184434.3a29c0f9.kamezawa.hiroyu@jp.fujitsu.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.0.3 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5182 Lines: 162 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: 20100804 - fixed description in init/Kconfig Changelog: 20100730 - fixed rcu_read_unlock() placement. Signed-off-by: KAMEZAWA Hiroyuki --- init/Kconfig | 10 ++++++++++ mm/memcontrol.c | 48 ++++++++++++++++++++++++++++++++++-------------- 2 files changed, 44 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]; +} /* * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft * limit reclaim to prevent infinite loops, if they ever occur. @@ -1824,18 +1848,7 @@ static void mem_cgroup_cancel_charge(str * it's concern. (dropping refcnt from swap can be called against removed * memcg.) */ -static struct mem_cgroup *mem_cgroup_lookup(unsigned short id) -{ - struct cgroup_subsys_state *css; - /* ID 0 is unused ID */ - if (!id) - return NULL; - css = css_lookup(&mem_cgroup_subsys, id); - if (!css) - return NULL; - return container_of(css, struct mem_cgroup, css); -} struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page) { @@ -1856,7 +1869,7 @@ struct mem_cgroup *try_get_mem_cgroup_fr ent.val = page_private(page); id = lookup_swap_cgroup(ent); rcu_read_lock(); - mem = mem_cgroup_lookup(id); + mem = id_to_memcg(id); if (mem && !css_tryget(&mem->css)) mem = NULL; rcu_read_unlock(); @@ -2208,7 +2221,7 @@ __mem_cgroup_commit_charge_swapin(struct id = swap_cgroup_record(ent, 0); rcu_read_lock(); - memcg = mem_cgroup_lookup(id); + memcg = id_to_memcg(id); if (memcg) { /* * This recorded memcg can be obsolete one. So, avoid @@ -2472,7 +2485,7 @@ void mem_cgroup_uncharge_swap(swp_entry_ id = swap_cgroup_record(ent, 0); rcu_read_lock(); - memcg = mem_cgroup_lookup(id); + memcg = id_to_memcg(id); if (memcg) { /* * We uncharge this because swap is freed. @@ -3988,6 +4001,9 @@ static struct mem_cgroup *mem_cgroup_all struct mem_cgroup *mem; int size = sizeof(struct mem_cgroup); + if (atomic_read(&mem_cgroup_num) == NR_MEMCG_GROUPS) + return NULL; + /* Can be very big if MAX_NUMNODES is very big */ if (size < PAGE_SIZE) mem = kmalloc(size, GFP_KERNEL); @@ -4025,7 +4041,10 @@ static void __mem_cgroup_free(struct mem int node; mem_cgroup_remove_from_trees(mem); + /* No more lookup against this ID */ + mem_cgroups[css_id(&mem->css)] = NULL; free_css_id(&mem_cgroup_subsys, &mem->css); + atomic_dec(&mem_cgroup_num); for_each_node_state(node, N_POSSIBLE) free_mem_cgroup_per_zone_info(mem, node); @@ -4162,6 +4181,7 @@ mem_cgroup_create(struct cgroup_subsys * atomic_set(&mem->refcnt, 1); mem->move_charge_at_immigrate = 0; mutex_init(&mem->thresholds_lock); + atomic_inc(&mem_cgroup_num); return &mem->css; free_out: __mem_cgroup_free(mem); Index: mmotm-0727/init/Kconfig =================================================================== --- mmotm-0727.orig/init/Kconfig +++ mmotm-0727/init/Kconfig @@ -594,6 +594,16 @@ 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(a pointer per group) will be consumed. + menuconfig CGROUP_SCHED bool "Group CPU scheduler" depends on EXPERIMENTAL && CGROUPS -- 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/