On Wed, May 03, 2017 at 10:00:04AM -0700, Omar Sandoval wrote: > On Thu, May 04, 2017 at 12:55:30AM +0800, Ming Lei wrote: > > On Wed, May 03, 2017 at 09:29:36AM -0700, Omar Sandoval wrote: > > > On Fri, Apr 28, 2017 at 11:15:38PM +0800, Ming Lei wrote: > > > > When tag space of one device is big enough, we use hw tag > > > > directly for I/O scheduling. > > > > > > > > Now the decision is made if hw queue depth is not less than > > > > q->nr_requests and the tag set isn't shared. > > > > > > > > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> > > > > --- > > > > block/blk-mq-sched.c | 8 ++++++++ > > > > block/blk-mq-sched.h | 15 +++++++++++++++ > > > > block/blk-mq.c | 18 +++++++++++++++++- > > > > 3 files changed, 40 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c > > > > index 45a675f07b8b..4681e27c127e 100644 > > > > --- a/block/blk-mq-sched.c > > > > +++ b/block/blk-mq-sched.c > > > > @@ -507,6 +507,7 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e) > > > > struct elevator_queue *eq; > > > > unsigned int i; > > > > int ret; > > > > + bool auto_hw_tag; > > > > > > > > if (!e) { > > > > q->elevator = NULL; > > > > @@ -519,7 +520,14 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e) > > > > */ > > > > q->nr_requests = 2 * BLKDEV_MAX_RQ; > > > > > > > > + auto_hw_tag = blk_mq_sched_may_use_hw_tag(q); > > > > + > > > > queue_for_each_hw_ctx(q, hctx, i) { > > > > + if (auto_hw_tag) > > > > + hctx->flags |= BLK_MQ_F_SCHED_USE_HW_TAG; > > > > + else > > > > + hctx->flags &= ~BLK_MQ_F_SCHED_USE_HW_TAG; > > > > + > > > > ret = blk_mq_sched_alloc_tags(q, hctx, i); > > > > if (ret) > > > > goto err; > > > > > > I think you should also clear the BLK_MQ_F_SCHED_USE_HW_TAG flag in > > > blk_mq_exit_sched()? > > > > Looks not necessary since the flag is always evaluated in > > blk_mq_init_sched(). > > What if we're setting the scheduler to "none"? Then blk_mq_init_sched() > will go in here: > > if (!e) { > q->elevator = NULL; > return 0; > } Good catch, will clear the flag in blk_mq_exit_sched() in V2. Thanks, Ming