On Tue, Jul 28, 2020 at 02:24:38AM -0700, Sagi Grimberg wrote: > > > > I like the tagset based interface. But the idea of doing a per-hctx > > > allocation and wait doesn't seem very scalable. > > > > > > Paul, do you have any good idea for an interface that waits on > > > multiple srcu heads? As far as I can tell we could just have a single > > > global completion and counter, and each call_srcu would just just > > > decrement it and then the final one would do the wakeup. It would just > > > be great to figure out a way to keep the struct rcu_synchronize and > > > counter on stack to avoid an allocation. > > > > > > But if we can't do with an on-stack object I'd much rather just embedd > > > the rcu_head in the hw_ctx. > > > > I think we can do that, please see the following patch which is against Sagi's V5: > > I don't think you can send a single rcu_head to multiple call_srcu calls. OK, then one variant is to put the rcu_head into blk_mq_hw_ctx, and put rcu_synchronize into blk_mq_tag_set. Thanks, Ming
