Messages in this thread | | | Date | Thu, 4 Feb 2010 17:55:02 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH] memcg: use for each online for making sum of percpu counter |
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On Thu, 4 Feb 2010 13:57:43 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-02-04 14:36:45]: > > > Tested on mmotm-2010-02-03. > > > > Balbir-san, how about this patch ? It seems not so difficult as expected. > > > > == > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > > > memcg-use-for-each-online-cpus-for-making-sum-of-percpu-counter > > > > Now, memcg's percpu coutner uses for_each_possible_cpus() for > > handling cpu hotplug. But it adds some overhead on a server > > which has an additonal cpu hotplug slot which is not used. > > > > This patch adds cpu hotplug callback for memcg's percpu counter > > and make use of for_each_online_cpu(). > > > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > --- > > mm/memcontrol.c | 35 ++++++++++++++++++++++++++++++++--- > > 1 file changed, 32 insertions(+), 3 deletions(-) > > > > Index: mmotm-2.6.33-Feb3/mm/memcontrol.c > > =================================================================== > > --- mmotm-2.6.33-Feb3.orig/mm/memcontrol.c > > +++ mmotm-2.6.33-Feb3/mm/memcontrol.c > > @@ -223,6 +223,8 @@ struct mem_cgroup { > > */ > > unsigned long move_charge_at_immigrate; > > > > + /* list of all memcgs. currently used for cpu hotplug+percpu counter */ > > + struct list_head list; > > /* > > * percpu counter. > > */ > > @@ -504,7 +506,7 @@ static s64 mem_cgroup_read_stat(struct m > > int cpu; > > s64 val = 0; > > > > - for_each_possible_cpu(cpu) > > + for_each_online_cpu(cpu) > > val += per_cpu(mem->stat->count[idx], cpu); > > return val; > > } > > @@ -1405,17 +1407,37 @@ static void drain_all_stock_sync(void) > > atomic_dec(&memcg_drain_count); > > } > > > > -static int __cpuinit memcg_stock_cpu_callback(struct notifier_block *nb, > > +DEFINE_MUTEX(memcg_hotcpu_lock); > > +LIST_HEAD(memcg_hotcpu_list); > > + > > +static int __cpuinit memcg_cpu_unplug_callback(struct notifier_block *nb, > > unsigned long action, > > void *hcpu) > > { > > int cpu = (unsigned long)hcpu; > > + struct mem_cgroup *memcg; > > struct memcg_stock_pcp *stock; > > + int idx; > > + s64 val; > > > > if (action != CPU_DEAD) > > return NOTIFY_OK; > > stock = &per_cpu(memcg_stock, cpu); > > drain_stock(stock); > > + > > + /* Move dead percpu counter's value to online cpu */ > > + mutex_lock(&memcg_hotcpu_lock); > > + list_for_each_entry(memcg, &memcg_hotcpu_list, list) { > > + for (idx = MEM_CGROUP_STAT_CACHE; > > + idx <= MEM_CGROUP_STAT_SWAPOUT; > > + idx++) { > > Should we add a for_each_stat_idx() macro? > I used bare codes because EVENT_COUNTERs are not target.
> > + val = per_cpu(memcg->stat->count[idx], cpu); > > + per_cpu(memcg->stat->count[idx], cpu) = 0; > > + this_cpu_add(memcg->stat->count[idx], val); > > So the CPU that deals with the hotplug notification moves the stats to > its own counter? Seems fair enough. > yes. I hope there will be no requests to get per-cpu statitstics...
> > + } > > + } > > + mutex_unlock(&memcg_hotcpu_lock); > > + > > return NOTIFY_OK; > > } > > > > @@ -3626,6 +3648,10 @@ static struct mem_cgroup *mem_cgroup_all > > else > > vfree(mem); > > mem = NULL; > > + } else { > > + mutex_lock(&memcg_hotcpu_lock); > > + list_add(&mem->list, &memcg_hotcpu_list); > > + mutex_unlock(&memcg_hotcpu_lock); > > } > > return mem; > > } > > @@ -3651,6 +3677,9 @@ static void __mem_cgroup_free(struct mem > > for_each_node_state(node, N_POSSIBLE) > > free_mem_cgroup_per_zone_info(mem, node); > > > > + mutex_lock(&memcg_hotcpu_lock); > > + list_del(&mem->list); > > + mutex_unlock(&memcg_hotcpu_lock); > > free_percpu(mem->stat); > > if (sizeof(struct mem_cgroup) < PAGE_SIZE) > > kfree(mem); > > @@ -3753,7 +3782,7 @@ mem_cgroup_create(struct cgroup_subsys * > > &per_cpu(memcg_stock, cpu); > > INIT_WORK(&stock->work, drain_local_stock); > > } > > - hotcpu_notifier(memcg_stock_cpu_callback, 0); > > + hotcpu_notifier(memcg_cpu_unplug_callback, 0); > > } else { > > parent = mem_cgroup_from_cont(cont->parent); > > mem->use_hierarchy = parent->use_hierarchy; > > > > Looks good, but I've not tested it yet. > Ok, I just did small test of online/offline cpus.
Thanks, -Kame
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