Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751416AbaLOEXA (ORCPT ); Sun, 14 Dec 2014 23:23:00 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:34405 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750881AbaLOEW7 (ORCPT ); Sun, 14 Dec 2014 23:22:59 -0500 X-SecurityPolicyCheck: OK by SHieldMailChecker v2.2.3 X-SHieldMailCheckerPolicyVersion: FJ-ISEC-20140219-2 Message-ID: <548E5DE4.8080201@jp.fujitsu.com> Date: Mon, 15 Dec 2014 13:04:52 +0900 From: Kamezawa Hiroyuki User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Lai Jiangshan CC: , Tejun Heo , Yasuaki Ishimatsu , "Gu, Zheng" , tangchen Subject: Re: [PATCH 4/4] workqueue: handle change in cpu-node relationship. References: <1418379595-6281-1-git-send-email-laijs@cn.fujitsu.com> <548C68DA.20507@jp.fujitsu.com> <548C6B72.5080302@jp.fujitsu.com> <548E4388.5090308@cn.fujitsu.com> <548E4578.3070209@jp.fujitsu.com> <548E4BF7.3000605@cn.fujitsu.com> <548E4DBF.7090406@jp.fujitsu.com> <548E56DB.7090803@cn.fujitsu.com> In-Reply-To: <548E56DB.7090803@cn.fujitsu.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-SecurityPolicyCheck-GC: OK by FENCE-Mail Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2014/12/15 12:34), Lai Jiangshan wrote: > On 12/15/2014 10:55 AM, Kamezawa Hiroyuki wrote: >> (2014/12/15 11:48), Lai Jiangshan wrote: >>> On 12/15/2014 10:20 AM, Kamezawa Hiroyuki wrote: >>>> (2014/12/15 11:12), Lai Jiangshan wrote: >>>>> On 12/14/2014 12:38 AM, Kamezawa Hiroyuki wrote: >>>>>> Although workqueue detects relationship between cpu<->node at boot, >>>>>> it is finally determined in cpu_up(). >>>>>> This patch tries to update pool->node using online status of cpus. >>>>>> >>>>>> 1. When a node goes down, clear per-cpu pool's node attr. >>>>>> 2. When a cpu comes up, update per-cpu pool's node attr. >>>>>> 3. When a cpu comes up, update possinle node cpumask workqueue is using for sched. >>>>>> 4. Detect the best node for unbound pool's cpumask using the latest info. >>>>>> >>>>>> Signed-off-by: KAMEZAWA Hiroyuki >>>>>> --- >>>>>> kernel/workqueue.c | 67 ++++++++++++++++++++++++++++++++++++++++++------------ >>>>>> 1 file changed, 53 insertions(+), 14 deletions(-) >>>>>> >>>>>> diff --git a/kernel/workqueue.c b/kernel/workqueue.c >>>>>> index 07b4eb5..259b3ba 100644 >>>>>> --- a/kernel/workqueue.c >>>>>> +++ b/kernel/workqueue.c >>>>>> @@ -266,7 +266,8 @@ struct workqueue_struct { >>>>>> static struct kmem_cache *pwq_cache; >>>>>> >>>>>> static cpumask_var_t *wq_numa_possible_cpumask; >>>>>> - /* possible CPUs of each node */ >>>>>> + /* possible CPUs of each node initialized with possible info at boot. >>>>>> + but modified at cpu hotplug to be adjusted to real info. */ >>>>>> >>>>>> static bool wq_disable_numa; >>>>>> module_param_named(disable_numa, wq_disable_numa, bool, 0444); >>>>>> @@ -3449,6 +3450,31 @@ static void put_unbound_pool(struct worker_pool *pool) >>>>>> call_rcu_sched(&pool->rcu, rcu_free_pool); >>>>>> } >>>>>> >>>>>> +/* >>>>>> + * detect best node for given cpumask. >>>>>> + */ >>>>>> +static int pool_detect_best_node(const struct cpumask *cpumask) >>>>>> +{ >>>>>> + int node, best, match, selected; >>>>>> + static struct cpumask andmask; /* we're under mutex */ >>>>>> + >>>>>> + /* Is any node okay ? */ >>>>>> + if (!wq_numa_enabled || >>>>>> + cpumask_subset(cpu_online_mask, cpumask)) >>>>>> + return NUMA_NO_NODE; >>>>>> + best = 0; >>>>>> + selected = NUMA_NO_NODE; >>>>>> + /* select a node which contains the most cpu of cpumask */ >>>>>> + for_each_node_state(node, N_ONLINE) { >>>>>> + cpumask_and(&andmask, cpumask, cpumask_of_node(node)); >>>>>> + match = cpumask_weight(&andmask); >>>>>> + if (match > best) >>>>>> + selected = node; >>>>>> + } >>>>>> + return selected; >>>>>> +} >>>>>> + >>>>>> + >>>>>> /** >>>>>> * get_unbound_pool - get a worker_pool with the specified attributes >>>>>> * @attrs: the attributes of the worker_pool to get >>>>>> @@ -3467,7 +3493,6 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs) >>>>>> { >>>>>> u32 hash = wqattrs_hash(attrs); >>>>>> struct worker_pool *pool; >>>>>> - int node; >>>>>> >>>>>> lockdep_assert_held(&wq_pool_mutex); >>>>>> >>>>>> @@ -3492,17 +3517,7 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs) >>>>>> * 'struct workqueue_attrs' comments for detail. >>>>>> */ >>>>>> pool->attrs->no_numa = false; >>>>>> - >>>>>> - /* if cpumask is contained inside a NUMA node, we belong to that node */ >>>>>> - if (wq_numa_enabled) { >>>>>> - for_each_node(node) { >>>>>> - if (cpumask_subset(pool->attrs->cpumask, >>>>>> - wq_numa_possible_cpumask[node])) { >>>>>> - pool->node = node; >>>>>> - break; >>>>>> - } >>>>>> - } >>>>>> - } >>>>>> + pool->node = pool_detect_best_node(pool->attrs->cpumask); >>>>>> >>>>>> if (worker_pool_assign_id(pool) < 0) >>>>>> goto fail; >>>>>> @@ -4567,7 +4582,7 @@ static int workqueue_cpu_up_callback(struct notifier_block *nfb, >>>>>> int cpu = (unsigned long)hcpu; >>>>>> struct worker_pool *pool; >>>>>> struct workqueue_struct *wq; >>>>>> - int pi; >>>>>> + int pi, node; >>>>>> >>>>>> switch (action & ~CPU_TASKS_FROZEN) { >>>>>> case CPU_UP_PREPARE: >>>>>> @@ -4583,6 +4598,16 @@ static int workqueue_cpu_up_callback(struct notifier_block *nfb, >>>>>> case CPU_ONLINE: >>>>>> mutex_lock(&wq_pool_mutex); >>>>>> >>>>>> + /* now cpu <-> node info is established, update the info. */ >>>>>> + if (!wq_disable_numa) { >>>>> >>>>> >>>>> >>>>>> + for_each_node_state(node, N_POSSIBLE) >>>>>> + cpumask_clear_cpu(cpu, >>>>>> + wq_numa_possible_cpumask[node]); >>>>> >>>>> The wq code try to reuse the origin pwqs/pools when the node still have cpu online. >>>>> these 3 lines of code will cause the origin pwqs/pools be on the road of dying, and >>>>> create a new set of pwqs/pools. >>>> >>>> because the result of wq_calc_node_cpumask() changes ? >>> >>> Yes. >>> >>>> Do you mean some comment should be added here ? or explaination for your reply for [3/4] ? >>> >>> this fix [4/4] breaks the original design. >>> >> >> I'm sorry that I can't understand what this patch breaks. > > the pwqs/pools should be kept if the node still have cpu online. So, the fix's grand design should be 1. drop old pwq/pools only at node offline. 2. set proper pool->node based on online node info. 3. update pool->node of per-cpu-pool at cpu ONLINE. Hm. (1) is done because cpumask_of_node() turns to be zero-filled after all cpus on a node offlined. But, cpu-to-node relationship cannot be available until a cpu get onlined. It changes at every cpu onlining. So, at node online, refleshing cpumasks of workqueues only after _all_ cpus on node are onlined seems to be the only way but I'm not sure how to get a mask of possible cpus on a node. Possible another way may be using auto numa balancing's numa node hint for worker scheduling. Do you have any idea ? Thanks, -Kame -- 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/