From 5f1a8c1bc724498ff32acbd59ed5263275676b9d Mon Sep 17 00:00:00 2001 From: Steffen Klassert Date: Wed, 7 Jul 2010 15:32:39 +0200 Subject: padata: simplify serialization mechanism We count the number of processed objects on a percpu basis, so we need to go through all the percpu reorder queues to calculate the sequence number of the next object that needs serialization. This patch changes this to count the number of processed objects global. So we can calculate the sequence number and the percpu reorder queue of the next object that needs serialization without searching through the percpu reorder queues. This avoids some accesses to memory of foreign cpus. Signed-off-by: Steffen Klassert Signed-off-by: Herbert Xu --- kernel/padata.c | 71 +++++++++++++++------------------------------------------ 1 file changed, 19 insertions(+), 52 deletions(-) (limited to 'kernel') diff --git a/kernel/padata.c b/kernel/padata.c index ae8defcf062..450d67d394b 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -170,79 +170,47 @@ EXPORT_SYMBOL(padata_do_parallel); */ static struct padata_priv *padata_get_next(struct parallel_data *pd) { - int cpu, num_cpus, empty, calc_seq_nr; - int seq_nr, next_nr, overrun, next_overrun; + int cpu, num_cpus; + int next_nr, next_index; struct padata_queue *queue, *next_queue; struct padata_priv *padata; struct padata_list *reorder; - empty = 0; - next_nr = -1; - next_overrun = 0; - next_queue = NULL; - num_cpus = cpumask_weight(pd->cpumask); - for_each_cpu(cpu, pd->cpumask) { - queue = per_cpu_ptr(pd->queue, cpu); - reorder = &queue->reorder; - - /* - * Calculate the seq_nr of the object that should be - * next in this reorder queue. - */ - overrun = 0; - calc_seq_nr = (atomic_read(&queue->num_obj) * num_cpus) - + queue->cpu_index; - - if (unlikely(calc_seq_nr > pd->max_seq_nr)) { - calc_seq_nr = calc_seq_nr - pd->max_seq_nr - 1; - overrun = 1; - } - - if (!list_empty(&reorder->list)) { - padata = list_entry(reorder->list.next, - struct padata_priv, list); - - seq_nr = padata->seq_nr; - BUG_ON(calc_seq_nr != seq_nr); - } else { - seq_nr = calc_seq_nr; - empty++; - } - - if (next_nr < 0 || seq_nr < next_nr - || (next_overrun && !overrun)) { - next_nr = seq_nr; - next_overrun = overrun; - next_queue = queue; - } + /* + * Calculate the percpu reorder queue and the sequence + * number of the next object. + */ + next_nr = pd->processed; + next_index = next_nr % num_cpus; + cpu = padata_index_to_cpu(pd, next_index); + next_queue = per_cpu_ptr(pd->queue, cpu); + + if (unlikely(next_nr > pd->max_seq_nr)) { + next_nr = next_nr - pd->max_seq_nr - 1; + next_index = next_nr % num_cpus; + cpu = padata_index_to_cpu(pd, next_index); + next_queue = per_cpu_ptr(pd->queue, cpu); + pd->processed = 0; } padata = NULL; - if (empty == num_cpus) - goto out; - reorder = &next_queue->reorder; if (!list_empty(&reorder->list)) { padata = list_entry(reorder->list.next, struct padata_priv, list); - if (unlikely(next_overrun)) { - for_each_cpu(cpu, pd->cpumask) { - queue = per_cpu_ptr(pd->queue, cpu); - atomic_set(&queue->num_obj, 0); - } - } + BUG_ON(next_nr != padata->seq_nr); spin_lock(&reorder->lock); list_del_init(&padata->list); atomic_dec(&pd->reorder_objects); spin_unlock(&reorder->lock); - atomic_inc(&next_queue->num_obj); + pd->processed++; goto out; } @@ -430,7 +398,6 @@ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst, INIT_WORK(&queue->pwork, padata_parallel_worker); INIT_WORK(&queue->swork, padata_serial_worker); - atomic_set(&queue->num_obj, 0); } num_cpus = cpumask_weight(pd->cpumask); -- cgit v1.2.3-70-g09d2