Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751468AbZJIEQ3 (ORCPT ); Fri, 9 Oct 2009 00:16:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751337AbZJIEQ3 (ORCPT ); Fri, 9 Oct 2009 00:16:29 -0400 Received: from e28smtp08.in.ibm.com ([59.145.155.8]:43359 "EHLO e28smtp08.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751190AbZJIEQ2 (ORCPT ); Fri, 9 Oct 2009 00:16:28 -0400 Date: Fri, 9 Oct 2009 09:45:36 +0530 From: Balbir Singh To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "nishimura@mxp.nes.nec.co.jp" Subject: Re: [PATCH 2/2] memcg: coalescing charges per cpu Message-ID: <20091009041535.GO6818@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20091002135531.3b5abf5c.kamezawa.hiroyu@jp.fujitsu.com> <20091002140343.ae63e932.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20091002140343.ae63e932.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8121 Lines: 265 * KAMEZAWA Hiroyuki [2009-10-02 14:03:43]: > From: KAMEZAWA Hiroyuki > > This is a patch for coalescing access to res_counter at charging by > percpu caching. At charge, memcg charges 64pages and remember it in > percpu cache. Because it's cache, drain/flush is done if necessary. > > This version uses public percpu area. > 2 benefits of using public percpu area. > 1. Sum of stocked charge in the system is limited to # of cpus > not to the number of memcg. This shows better synchonization. > 2. drain code for flush/cpuhotplug is very easy (and quick) > > The most important point of this patch is that we never touch res_counter > in fast path. The res_counter is system-wide shared counter which is modified > very frequently. We shouldn't touch it as far as we can for avoiding > false sharing. > > Changelog (new): > - rabased onto the latest mmotm > Changelog (old): > - moved charge size check before __GFP_WAIT check for avoiding unnecesary > - added asynchronous flush routine. > - fixed bugs pointed out by Nishimura-san. > > Signed-off-by: KAMEZAWA Hiroyuki > --- > mm/memcontrol.c | 126 +++++++++++++++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 120 insertions(+), 6 deletions(-) > > Index: mmotm-2.6.31-Sep28/mm/memcontrol.c > =================================================================== > --- mmotm-2.6.31-Sep28.orig/mm/memcontrol.c > +++ mmotm-2.6.31-Sep28/mm/memcontrol.c > @@ -38,6 +38,7 @@ > #include > #include > #include > +#include > #include "internal.h" > > #include > @@ -275,6 +276,7 @@ enum charge_type { > static void mem_cgroup_get(struct mem_cgroup *mem); > static void mem_cgroup_put(struct mem_cgroup *mem); > static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem); > +static void drain_all_stock_async(void); > > static struct mem_cgroup_per_zone * > mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid) > @@ -1137,6 +1139,8 @@ static int mem_cgroup_hierarchical_recla > victim = mem_cgroup_select_victim(root_mem); > if (victim == root_mem) { > loop++; > + if (loop >= 1) > + drain_all_stock_async(); > if (loop >= 2) { > /* > * If we have not been able to reclaim > @@ -1258,6 +1262,103 @@ done: > unlock_page_cgroup(pc); > } > > +/* size of first charge trial. "32" comes from vmscan.c's magic value */ > +#define CHARGE_SIZE (32 * PAGE_SIZE) Should this then be SWAP_CLUSTER_MAX instead of 32? > +struct memcg_stock_pcp { > + struct mem_cgroup *cached; > + int charge; > + struct work_struct work; > +}; > +static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock); > +static DEFINE_MUTEX(memcg_drain_mutex); > + > +static bool consume_stock(struct mem_cgroup *mem) > +{ > + struct memcg_stock_pcp *stock; > + bool ret = true; > + > + stock = &get_cpu_var(memcg_stock); > + if (mem == stock->cached && stock->charge) > + stock->charge -= PAGE_SIZE; > + else > + ret = false; > + put_cpu_var(memcg_stock); > + return ret; > +} Shouldn't consume stock and routines below check for memcg_is_root()? > + > +static void drain_stock(struct memcg_stock_pcp *stock) > +{ > + struct mem_cgroup *old = stock->cached; > + > + if (stock->charge) { > + res_counter_uncharge(&old->res, stock->charge); > + if (do_swap_account) > + res_counter_uncharge(&old->memsw, stock->charge); > + } > + stock->cached = NULL; > + stock->charge = 0; > +} > + > +static void drain_local_stock(struct work_struct *dummy) > +{ > + struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock); > + drain_stock(stock); > + put_cpu_var(memcg_stock); > +} > + > +static void refill_stock(struct mem_cgroup *mem, int val) > +{ > + struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock); > + > + if (stock->cached != mem) { > + drain_stock(stock); > + stock->cached = mem; > + } More comments here would help > + stock->charge += val; > + put_cpu_var(memcg_stock); > +} > + > +static void drain_all_stock_async(void) > +{ > + int cpu; > + /* Contention means someone tries to flush. */ > + if (!mutex_trylock(&memcg_drain_mutex)) > + return; > + for_each_online_cpu(cpu) { > + struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu); > + if (work_pending(&stock->work)) > + continue; > + INIT_WORK(&stock->work, drain_local_stock); > + schedule_work_on(cpu, &stock->work); > + } > + mutex_unlock(&memcg_drain_mutex); > + /* We don't wait for flush_work */ > +} > + > +static void drain_all_stock_sync(void) > +{ > + /* called when force_empty is called */ > + mutex_lock(&memcg_drain_mutex); > + schedule_on_each_cpu(drain_local_stock); > + mutex_unlock(&memcg_drain_mutex); > +} > + > +static int __cpuinit memcg_stock_cpu_callback(struct notifier_block *nb, > + unsigned long action, > + void *hcpu) > +{ > +#ifdef CONFIG_HOTPLUG_CPU > + int cpu = (unsigned long)hcpu; > + struct memcg_stock_pcp *stock; > + > + if (action != CPU_DEAD) > + return NOTIFY_OK; > + stock = &per_cpu(memcg_stock, cpu); > + drain_stock(stock); > +#endif > + return NOTIFY_OK; > +} > + > /* > * Unlike exported interface, "oom" parameter is added. if oom==true, > * oom-killer can be invoked. > @@ -1269,6 +1370,7 @@ static int __mem_cgroup_try_charge(struc > struct mem_cgroup *mem, *mem_over_limit; > int nr_retries = MEM_CGROUP_RECLAIM_RETRIES; > struct res_counter *fail_res; > + int csize = CHARGE_SIZE; > > if (unlikely(test_thread_flag(TIF_MEMDIE))) { > /* Don't account this! */ > @@ -1293,23 +1395,25 @@ static int __mem_cgroup_try_charge(struc > return 0; > > VM_BUG_ON(css_is_removed(&mem->css)); > + if (mem_cgroup_is_root(mem)) > + goto done; > > while (1) { > int ret = 0; > unsigned long flags = 0; > > - if (mem_cgroup_is_root(mem)) > - goto done; > - ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res); > + if (consume_stock(mem)) > + goto charged; > + > + ret = res_counter_charge(&mem->res, csize, &fail_res); > if (likely(!ret)) { > if (!do_swap_account) > break; > - ret = res_counter_charge(&mem->memsw, PAGE_SIZE, > - &fail_res); > + ret = res_counter_charge(&mem->memsw, csize, &fail_res); > if (likely(!ret)) > break; > /* mem+swap counter fails */ > - res_counter_uncharge(&mem->res, PAGE_SIZE); > + res_counter_uncharge(&mem->res, csize); > flags |= MEM_CGROUP_RECLAIM_NOSWAP; > mem_over_limit = mem_cgroup_from_res_counter(fail_res, > memsw); > @@ -1318,6 +1422,11 @@ static int __mem_cgroup_try_charge(struc > mem_over_limit = mem_cgroup_from_res_counter(fail_res, > res); > > + /* reduce request size and retry */ > + if (csize > PAGE_SIZE) { > + csize = PAGE_SIZE; > + continue; > + } > if (!(gfp_mask & __GFP_WAIT)) > goto nomem; > > @@ -1347,6 +1456,9 @@ static int __mem_cgroup_try_charge(struc > goto nomem; > } > } > + if (csize > PAGE_SIZE) > + refill_stock(mem, csize - PAGE_SIZE); > +charged: > /* > * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree. > * if they exceeds softlimit. > @@ -2463,6 +2575,7 @@ move_account: > goto out; > /* This is for making all *used* pages to be on LRU. */ > lru_add_drain_all(); > + drain_all_stock_sync(); > ret = 0; > for_each_node_state(node, N_HIGH_MEMORY) { > for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) { > @@ -3181,6 +3294,7 @@ mem_cgroup_create(struct cgroup_subsys * > root_mem_cgroup = mem; > if (mem_cgroup_soft_limit_tree_init()) > goto free_out; > + hotcpu_notifier(memcg_stock_cpu_callback, 0); > > } else { > parent = mem_cgroup_from_cont(cont->parent); > I tested earlier versions of the patchset and they worked absolutely fine for me! 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