Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932242Ab0HaHOZ (ORCPT ); Tue, 31 Aug 2010 03:14:25 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:35708 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932172Ab0HaHOY (ORCPT ); Tue, 31 Aug 2010 03:14:24 -0400 Date: Tue, 31 Aug 2010 12:44:14 +0530 From: Balbir Singh To: KAMEZAWA Hiroyuki Cc: linux-mm@kvack.org, "nishimura@mxp.nes.nec.co.jp" , gthelen@google.com, m-ikeda@ds.jp.nec.com, "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" , "menage@google.com" , "lizf@cn.fujitsu.com" Subject: Re: [PATCH 2/5] memcg: quick memcg lookup array Message-ID: <20100831071414.GN32680@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20100825170435.15f8eb73.kamezawa.hiroyu@jp.fujitsu.com> <20100825170741.f1f0a220.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20100825170741.f1f0a220.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7841 Lines: 248 * KAMEZAWA Hiroyuki [2010-08-25 17:07:41]: > 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: 20100825 > - applied comments. > > Changelog: 20100811 > - adjusted onto mmotm-2010-08-11 > - fixed RCU related parts. > - use attach_id() callback. > > 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 | 75 +++++++++++++++++++++++++++++++++++++++++--------------- > 2 files changed, 65 insertions(+), 20 deletions(-) > > Index: mmotm-0811/mm/memcontrol.c > =================================================================== > --- mmotm-0811.orig/mm/memcontrol.c > +++ mmotm-0811/mm/memcontrol.c > @@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct > */ > struct mem_cgroup { > struct cgroup_subsys_state css; > + int valid; /* for checking validness under RCU access.*/ > /* > * the counter to account for memory usage > */ > @@ -294,6 +295,29 @@ 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; > + > +/* Must be called under rcu_read_lock */ > +static struct mem_cgroup *id_to_memcg(unsigned short id) > +{ > + struct mem_cgroup *mem; > + /* see mem_cgroup_free() */ > + mem = rcu_dereference_check(mem_cgroups[id], rcu_read_lock_held()); > + if (likely(mem && mem->valid)) > + return mem; > + return NULL; > +} > + > +static void register_memcg_id(struct mem_cgroup *mem) > +{ > + int id = css_id(&mem->css); > + rcu_assign_pointer(mem_cgroups[id], mem); > + VM_BUG_ON(!mem->valid); > +} > + > /* > * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft > * limit reclaim to prevent infinite loops, if they ever occur. > @@ -1847,18 +1871,7 @@ 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) > { > @@ -1879,7 +1892,7 @@ 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(); > @@ -2231,7 +2244,7 @@ __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 > @@ -2240,9 +2253,10 @@ __mem_cgroup_commit_charge_swapin(struct > if (!mem_cgroup_is_root(memcg)) > res_counter_uncharge(&memcg->memsw, PAGE_SIZE); > mem_cgroup_swap_statistics(memcg, false); > + rcu_read_unlock(); > mem_cgroup_put(memcg); > - } > - rcu_read_unlock(); > + } else > + rcu_read_unlock(); > } > /* > * At swapin, we may charge account against cgroup which has no tasks. > @@ -2495,7 +2509,7 @@ 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. > @@ -2504,9 +2518,10 @@ void mem_cgroup_uncharge_swap(swp_entry_ > if (!mem_cgroup_is_root(memcg)) > res_counter_uncharge(&memcg->memsw, PAGE_SIZE); > mem_cgroup_swap_statistics(memcg, false); > + rcu_read_unlock(); > mem_cgroup_put(memcg); > - } > - rcu_read_unlock(); > + } else > + rcu_read_unlock(); > } > > /** > @@ -4010,6 +4025,9 @@ 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); > @@ -4020,6 +4038,7 @@ static struct mem_cgroup *mem_cgroup_all > return NULL; > > memset(mem, 0, size); > + mem->valid = 1; > mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu); > if (!mem->stat) { > if (size < PAGE_SIZE) > @@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem > mem_cgroup_remove_from_trees(mem); > 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); > > @@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem > vfree(mem); > } > > +static void mem_cgroup_free(struct mem_cgroup *mem) > +{ > + /* No more lookup */ > + mem->valid = 0; > + rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL); > + /* > + * Because we call vfree() etc...use synchronize_rcu() rather than > + * call_rcu(); > + */ > + synchronize_rcu(); > + __mem_cgroup_free(mem); > +} > + > static void mem_cgroup_get(struct mem_cgroup *mem) > { > atomic_inc(&mem->refcnt); > @@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_ > { > if (atomic_sub_and_test(count, &mem->refcnt)) { > struct mem_cgroup *parent = parent_mem_cgroup(mem); > - __mem_cgroup_free(mem); > + mem_cgroup_free(mem); > if (parent) > mem_cgroup_put(parent); > } > @@ -4189,9 +4222,11 @@ 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); > + register_memcg_id(mem); > return &mem->css; > free_out: > - __mem_cgroup_free(mem); > + mem_cgroup_free(mem); > root_mem_cgroup = NULL; > return ERR_PTR(error); > } > Index: mmotm-0811/init/Kconfig > =================================================================== > --- mmotm-0811.orig/init/Kconfig > +++ mmotm-0811/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. > + Looks good, quick thought - should we expost memcg->id to user space through a config file? I don't see any reason at this point, unless we do it for all controllers. -- Three Cheers, Balbir -- 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/