On Mon, Nov 22, 2021 at 10:07:24AM +0200, Sagi Grimberg wrote: > > > On 11/19/21 4:18 AM, Ming Lei wrote: > > Chao Leng reported that in case of lots of namespaces, it may take quite a > > while for nvme_stop_queues() to quiesce all namespace queues. > > > > Improve nvme_stop_queues() by running quiesce in parallel, and just wait > > once if global quiesce wait is allowed. > > > > Link: https://lore.kernel.org/linux-block/cc732195-c053-9ce4-e1a7-e7f6dcf762ac@xxxxxxxxxx/ > > Reported-by: Chao Leng <lengchao@xxxxxxxxxx> > > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> > > --- > > drivers/nvme/host/core.c | 9 ++++++--- > > 1 file changed, 6 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > > index 4b5de8f5435a..06741d3ed72b 100644 > > --- a/drivers/nvme/host/core.c > > +++ b/drivers/nvme/host/core.c > > @@ -4517,9 +4517,7 @@ static void nvme_start_ns_queue(struct nvme_ns *ns) > > static void nvme_stop_ns_queue(struct nvme_ns *ns) > > { > > if (!test_and_set_bit(NVME_NS_STOPPED, &ns->flags)) > > - blk_mq_quiesce_queue(ns->queue); > > - else > > - blk_mq_wait_quiesce_done(ns->queue); > > + blk_mq_quiesce_queue_nowait(ns->queue); > > } > > /* > > @@ -4620,6 +4618,11 @@ void nvme_stop_queues(struct nvme_ctrl *ctrl) > > down_read(&ctrl->namespaces_rwsem); > > list_for_each_entry(ns, &ctrl->namespaces, list) > > nvme_stop_ns_queue(ns); > > + list_for_each_entry(ns, &ctrl->namespaces, list) { > > + blk_mq_wait_quiesce_done(ns->queue); > > + if (blk_mq_global_quiesce_wait(ns->queue)) > > + break; > > + } > > up_read(&ctrl->namespaces_rwsem); > > > Can you quantify how much of a difference it is to do rcu_read_unlock() > for every queue? The big improvement here is that it is done in parallel > instead of serially. Just wandering if it is worth the less than elegant > interface... The biggest improvement is N * synchronize_rcu() -> 1 * synchronize_rcu() in case of non blocking, that is what Chao Leng complained before. Even for blocking case, the parallel quiesce is still good, such as, when one synchronize_srcu() is done, other srcu syncs should be done usually too. thanks, Ming
