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charset=us-ascii Content-Disposition: inline X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: C5AFE20003 X-Stat-Signature: k3sw6axhidoi6csmc3qpgd3xig4dtxtf X-Rspam-User: X-HE-Tag: 1775089367-214288 X-HE-Meta: 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 JELHwr2v XX/GRbC51v56r42Z6K8HrURzWfbA6AuNQjEQcoXrq2N/9guvuCHX3tSFVhV+TQ9mH6gLka4OyuqVVraSwM/1hfJ8P+yhgehywsoUHUUSh5l9Po2OYJ5+ks/zOuPmDhkPRO5RxBY+Q8HEvaquLrFjDjvjAD9ntSWntqNq1QB7QrK6DY28E6/IWtxfWsZUJz9QwUqnJbphduB+UQw4OC6hzvyfewlR9ktftfpGN0/5IWSp46Kx06jKXe5XWRtNEex9pNbvEKJVIyMBJQl7iFedPUjlDq4V3cOJodWjqNR1yuEz2c6KTjxvHPM4CBXIVCWeLGBfKQlxSjrWCoPVRRQPIOTNNpwATx4pwAwy6+/KcO6nrTxU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 04/01/26 at 05:47pm, Baoquan He wrote: > On 03/31/26 at 10:23pm, Uladzislau Rezki (Sony) wrote: > > drain_vmap_area_work() function can take >10ms to complete > > when there are many accumulated vmap areas in a system with > > high CPU count, causing workqueue watchdog warnings when run > > via schedule_work(): > > > > workqueue: drain_vmap_area_work hogged CPU for >10000us > > > > Move the top-level drain work to a dedicated WQ_UNBOUND > > workqueue so the scheduler can run this background work > > on any available CPU, improving responsiveness. Use the > > WQ_MEM_RECLAIM to ensure forward progress under memory > > pressure. > > > > Move purge helpers to separate WQ_UNBOUND | WQ_MEM_RECLAIM > > workqueue. This allows drain_vmap_work to wait for helpers > > completion without creating dependency on the same rescuer > > thread and avoid a potential parent/child deadlock. > ...snip... > > @@ -2385,29 +2390,31 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end, > > nr_purge_helpers = atomic_long_read(&vmap_lazy_nr) / lazy_max_pages(); > > nr_purge_helpers = clamp(nr_purge_helpers, 1U, nr_purge_nodes) - 1; > > > > - for_each_cpu(i, &purge_nodes) { > > - vn = &vmap_nodes[i]; > > + for_each_vmap_node(vn) { > > + vn->work_queued = false; > > + > > + if (list_empty(&vn->purge_list)) > > + continue; > > > > if (nr_purge_helpers > 0) { > > INIT_WORK(&vn->purge_work, purge_vmap_node); > > + vn->work_queued = schedule_drain_vmap_work( > > + READ_ONCE(drain_vmap_helpers_wq), &vn->purge_work); > > The new schedule_drain_vmap_work() could submit all purge_work on one > CPU, do we need use queue_work_on(cpu, wq, work) instead? Forgot the specified WQ_UNBOUND on alloc_workqueue(), sorry for the noise. Then this patch looks great to me. > > > > > - if (cpumask_test_cpu(i, cpu_online_mask)) > > - schedule_work_on(i, &vn->purge_work); > > - else > > - schedule_work(&vn->purge_work); > > - > > - nr_purge_helpers--; > > - } else { > > - vn->purge_work.func = NULL; > > - purge_vmap_node(&vn->purge_work); > > - nr_purged_areas += vn->nr_purged; > > + if (vn->work_queued) { > > + nr_purge_helpers--; > > + continue; > > + } > > } > > - } > > > > - for_each_cpu(i, &purge_nodes) { > > - vn = &vmap_nodes[i]; > > + /* Sync path. Process locally. */ > > + purge_vmap_node(&vn->purge_work); > > + nr_purged_areas += vn->nr_purged; > > + } > > > > - if (vn->purge_work.func) { > > + /* Wait for completion if queued any. */ > > + for_each_vmap_node(vn) { > > + if (vn->work_queued) { > > flush_work(&vn->purge_work); > > nr_purged_areas += vn->nr_purged; > > } > ...snip... > > + > > +static int __init vmalloc_init_workqueue(void) > > +{ > > + struct workqueue_struct *drain_wq, *helpers_wq; > > Maybe there's one local variable is enough like below: > > struct workqueue_struct *wq; > unsigned int flags = WQ_UNBOUND | WQ_MEM_RECLAIM; > > wq = alloc_workqueue("vmap_drain", flags, 0); > WARN_ON_ONCE(wq == NULL); > WRITE_ONCE(drain_vmap_wq, wq); > > wq = alloc_workqueue("vmap_drain_helpers", flags, 0); > WARN_ON_ONCE(wq == NULL); > WRITE_ONCE(drain_vmap_helpers_wq, wq); > > return 0; > } > > Just personal preference on nitpick, not strong opionion. >