From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: + padata-allocate-work-structures-for-parallel-jobs-from-a-pool.patch added to -mm tree Date: Wed, 20 May 2020 16:31:23 -0700 Message-ID: <20200520233123.XxkjRWSJ5%akpm@linux-foundation.org> References: <20200513175005.1f4839360c18c0238df292d1@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:57224 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728552AbgETXb0 (ORCPT ); Wed, 20 May 2020 19:31:26 -0400 In-Reply-To: <20200513175005.1f4839360c18c0238df292d1@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: alex.williamson@redhat.com, alexander.h.duyck@linux.intel.com, corbet@lwn.net, dan.j.williams@intel.com, daniel.m.jordan@oracle.com, dave.hansen@linux.intel.com, david@redhat.com, elliott@hpe.com, herbert@gondor.apana.org.au, jgg@ziepe.ca, josh@joshtriplett.org, ktkhai@virtuozzo.com, mhocko@kernel.org, mm-commits@vger.kernel.org, pasha.tatashin@soleen.com, pavel@ucw.cz, peterz@infradead.org, rdunlap@infradead.org, shile.zhang@linux.alibaba.com, steffen.klassert@secunet.com, steven.sistare@oracle.com, tj@kernel.org, ziy@nvidia.com The patch titled Subject: padata: allocate work structures for parallel jobs from a pool has been added to the -mm tree. Its filename is padata-allocate-work-structures-for-parallel-jobs-from-a-pool.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/padata-allocate-work-structures-for-parallel-jobs-from-a-pool.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/padata-allocate-work-structures-for-parallel-jobs-from-a-pool.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Daniel Jordan Subject: padata: allocate work structures for parallel jobs from a pool padata allocates per-CPU, per-instance work structs for parallel jobs. A do_parallel call assigns a job to a sequence number and hashes the number to a CPU, where the job will eventually run using the corresponding work. This approach fit with how padata used to bind a job to each CPU round-robin, makes less sense after commit bfde23ce200e6 ("padata: unbind parallel jobs from specific CPUs") because a work isn't bound to a particular CPU anymore, and isn't needed at all for multithreaded jobs because they don't have sequence numbers. Replace the per-CPU works with a preallocated pool, which allows sharing them between existing padata users and the upcoming multithreaded user. The pool will also facilitate setting NUMA-aware concurrency limits with later users. The pool is sized according to the number of possible CPUs. With this limit, MAX_OBJ_NUM no longer makes sense, so remove it. If the global pool is exhausted, a parallel job is run in the current task instead to throttle a system trying to do too much in parallel. Link: http://lkml.kernel.org/r/20200520182645.1658949-4-daniel.m.jordan@oracle.com Signed-off-by: Daniel Jordan Cc: Alexander Duyck Cc: Alex Williamson Cc: Dan Williams Cc: Dave Hansen Cc: David Hildenbrand Cc: Herbert Xu Cc: Jason Gunthorpe Cc: Jonathan Corbet Cc: Josh Triplett Cc: Kirill Tkhai Cc: Michal Hocko Cc: Pavel Machek Cc: Pavel Tatashin Cc: Peter Zijlstra Cc: Randy Dunlap Cc: Robert Elliott Cc: Shile Zhang Cc: Steffen Klassert Cc: Steven Sistare Cc: Tejun Heo Cc: Zi Yan Signed-off-by: Andrew Morton --- include/linux/padata.h | 8 -- kernel/padata.c | 118 +++++++++++++++++++++++++-------------- 2 files changed, 78 insertions(+), 48 deletions(-) --- a/include/linux/padata.h~padata-allocate-work-structures-for-parallel-jobs-from-a-pool +++ a/include/linux/padata.h @@ -24,7 +24,6 @@ * @list: List entry, to attach to the padata lists. * @pd: Pointer to the internal control structure. * @cb_cpu: Callback cpu for serializatioon. - * @cpu: Cpu for parallelization. * @seq_nr: Sequence number of the parallelized data object. * @info: Used to pass information from the parallel to the serial function. * @parallel: Parallel execution function. @@ -34,7 +33,6 @@ struct padata_priv { struct list_head list; struct parallel_data *pd; int cb_cpu; - int cpu; unsigned int seq_nr; int info; void (*parallel)(struct padata_priv *padata); @@ -68,15 +66,11 @@ struct padata_serial_queue { /** * struct padata_parallel_queue - The percpu padata parallel queue * - * @parallel: List to wait for parallelization. * @reorder: List to wait for reordering after parallel processing. - * @work: work struct for parallelization. * @num_obj: Number of objects that are processed by this cpu. */ struct padata_parallel_queue { - struct padata_list parallel; struct padata_list reorder; - struct work_struct work; atomic_t num_obj; }; @@ -111,7 +105,7 @@ struct parallel_data { struct padata_parallel_queue __percpu *pqueue; struct padata_serial_queue __percpu *squeue; atomic_t refcnt; - atomic_t seq_nr; + unsigned int seq_nr; unsigned int processed; int cpu; struct padata_cpumask cpumask; --- a/kernel/padata.c~padata-allocate-work-structures-for-parallel-jobs-from-a-pool +++ a/kernel/padata.c @@ -32,7 +32,15 @@ #include #include -#define MAX_OBJ_NUM 1000 +struct padata_work { + struct work_struct pw_work; + struct list_head pw_list; /* padata_free_works linkage */ + void *pw_data; +}; + +static DEFINE_SPINLOCK(padata_works_lock); +static struct padata_work *padata_works; +static LIST_HEAD(padata_free_works); static void padata_free_pd(struct parallel_data *pd); @@ -58,30 +66,44 @@ static int padata_cpu_hash(struct parall return padata_index_to_cpu(pd, cpu_index); } -static void padata_parallel_worker(struct work_struct *parallel_work) +static struct padata_work *padata_work_alloc(void) { - struct padata_parallel_queue *pqueue; - LIST_HEAD(local_list); + struct padata_work *pw; - local_bh_disable(); - pqueue = container_of(parallel_work, - struct padata_parallel_queue, work); + lockdep_assert_held(&padata_works_lock); - spin_lock(&pqueue->parallel.lock); - list_replace_init(&pqueue->parallel.list, &local_list); - spin_unlock(&pqueue->parallel.lock); + if (list_empty(&padata_free_works)) + return NULL; /* No more work items allowed to be queued. */ - while (!list_empty(&local_list)) { - struct padata_priv *padata; + pw = list_first_entry(&padata_free_works, struct padata_work, pw_list); + list_del(&pw->pw_list); + return pw; +} - padata = list_entry(local_list.next, - struct padata_priv, list); +static void padata_work_init(struct padata_work *pw, work_func_t work_fn, + void *data) +{ + INIT_WORK(&pw->pw_work, work_fn); + pw->pw_data = data; +} - list_del_init(&padata->list); +static void padata_work_free(struct padata_work *pw) +{ + lockdep_assert_held(&padata_works_lock); + list_add(&pw->pw_list, &padata_free_works); +} - padata->parallel(padata); - } +static void padata_parallel_worker(struct work_struct *parallel_work) +{ + struct padata_work *pw = container_of(parallel_work, struct padata_work, + pw_work); + struct padata_priv *padata = pw->pw_data; + local_bh_disable(); + padata->parallel(padata); + spin_lock(&padata_works_lock); + padata_work_free(pw); + spin_unlock(&padata_works_lock); local_bh_enable(); } @@ -105,9 +127,9 @@ int padata_do_parallel(struct padata_she struct padata_priv *padata, int *cb_cpu) { struct padata_instance *pinst = ps->pinst; - int i, cpu, cpu_index, target_cpu, err; - struct padata_parallel_queue *queue; + int i, cpu, cpu_index, err; struct parallel_data *pd; + struct padata_work *pw; rcu_read_lock_bh(); @@ -135,25 +157,25 @@ int padata_do_parallel(struct padata_she if ((pinst->flags & PADATA_RESET)) goto out; - if (atomic_read(&pd->refcnt) >= MAX_OBJ_NUM) - goto out; - - err = 0; atomic_inc(&pd->refcnt); padata->pd = pd; padata->cb_cpu = *cb_cpu; - padata->seq_nr = atomic_inc_return(&pd->seq_nr); - target_cpu = padata_cpu_hash(pd, padata->seq_nr); - padata->cpu = target_cpu; - queue = per_cpu_ptr(pd->pqueue, target_cpu); - - spin_lock(&queue->parallel.lock); - list_add_tail(&padata->list, &queue->parallel.list); - spin_unlock(&queue->parallel.lock); + rcu_read_unlock_bh(); - queue_work(pinst->parallel_wq, &queue->work); + spin_lock(&padata_works_lock); + padata->seq_nr = ++pd->seq_nr; + pw = padata_work_alloc(); + spin_unlock(&padata_works_lock); + if (pw) { + padata_work_init(pw, padata_parallel_worker, padata); + queue_work(pinst->parallel_wq, &pw->pw_work); + } else { + /* Maximum works limit exceeded, run in the current task. */ + padata->parallel(padata); + } + return 0; out: rcu_read_unlock_bh(); @@ -324,8 +346,9 @@ static void padata_serial_worker(struct void padata_do_serial(struct padata_priv *padata) { struct parallel_data *pd = padata->pd; + int hashed_cpu = padata_cpu_hash(pd, padata->seq_nr); struct padata_parallel_queue *pqueue = per_cpu_ptr(pd->pqueue, - padata->cpu); + hashed_cpu); struct padata_priv *cur; spin_lock(&pqueue->reorder.lock); @@ -416,8 +439,6 @@ static void padata_init_pqueues(struct p pqueue = per_cpu_ptr(pd->pqueue, cpu); __padata_list_init(&pqueue->reorder); - __padata_list_init(&pqueue->parallel); - INIT_WORK(&pqueue->work, padata_parallel_worker); atomic_set(&pqueue->num_obj, 0); } } @@ -451,7 +472,7 @@ static struct parallel_data *padata_allo padata_init_pqueues(pd); padata_init_squeues(pd); - atomic_set(&pd->seq_nr, -1); + pd->seq_nr = -1; atomic_set(&pd->refcnt, 1); spin_lock_init(&pd->lock); pd->cpu = cpumask_first(pd->cpumask.pcpu); @@ -1051,6 +1072,7 @@ EXPORT_SYMBOL(padata_free_shell); void __init padata_init(void) { + unsigned int i, possible_cpus; #ifdef CONFIG_HOTPLUG_CPU int ret; @@ -1062,13 +1084,27 @@ void __init padata_init(void) ret = cpuhp_setup_state_multi(CPUHP_PADATA_DEAD, "padata:dead", NULL, padata_cpu_dead); - if (ret < 0) { - cpuhp_remove_multi_state(hp_online); - goto err; - } + if (ret < 0) + goto remove_online_state; +#endif + + possible_cpus = num_possible_cpus(); + padata_works = kmalloc_array(possible_cpus, sizeof(struct padata_work), + GFP_KERNEL); + if (!padata_works) + goto remove_dead_state; + + for (i = 0; i < possible_cpus; ++i) + list_add(&padata_works[i].pw_list, &padata_free_works); return; + +remove_dead_state: +#ifdef CONFIG_HOTPLUG_CPU + cpuhp_remove_multi_state(CPUHP_PADATA_DEAD); +remove_online_state: + cpuhp_remove_multi_state(hp_online); err: - pr_warn("padata: initialization failed\n"); #endif + pr_warn("padata: initialization failed\n"); } _ Patches currently in -mm which might be from daniel.m.jordan@oracle.com are mm-call-touch_nmi_watchdog-on-max-order-boundaries-in-deferred-init.patch padata-remove-exit-routine.patch padata-initialize-earlier.patch padata-allocate-work-structures-for-parallel-jobs-from-a-pool.patch padata-add-basic-support-for-multithreaded-jobs.patch mm-parallelize-deferred_init_memmap.patch mm-make-deferred-inits-max-threads-arch-specific.patch padata-document-multithreaded-jobs.patch