On 12/15/2014 12:04 PM, Kamezawa Hiroyuki wrote: > (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 <kamezawa.hir...@jp.fujitsu.com> >>>>>>> --- >>>>>>> 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
It changes at every cpu being added which earlier than any cpu of the node will be online. > of workqueues only after _all_ cpus on node are onlined seems to be the only > way When _any_ cpu on the new node is onlining, _add_ cpus of the node were *added*, which means all cpu_to_node()s of the all cpus on new node ware updated. so we can check the updated information when up online. This is what my patchset did. > but I'm not sure how to get a mask of possible cpus on a node. like this: + for_each_possible_cpu(cpu) { + node = cpu_to_node(node); + if (node == new_node) + cpumask_set_cpu(cpu, wq_numa_possible_cpumask[new_node]); + } > > Possible another way may be using auto numa balancing's numa node hint for > worker scheduling. > > Do you have any idea ? Is it hard to keep the cpu-node relationship unchanged? You know that, all cpu ids, node ids are soft-ware logical id, we can change relationship between logic id and physical id but keep relationship among logical ids unchanged. > > Thanks, > -Kame > > > > > > > > > > > . > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/