On Mon, Aug 19, 2024 at 08:49:26AM GMT, Paul E. McKenney wrote: > On Mon, Aug 19, 2024 at 11:14:02AM -0400, Kent Overstreet wrote: > By "number of outstanding grace period sequence numbers" you mean > the number of outstanding grace period sequence numbers that have > memory blocks that have not yet been processed? If so, how could that > possibly matter more than the total number of memory blocks that have > not been processed, regardless of which grace-period number they are > associated with? Why would a huge number of memory blocks fail to > cause an OOM simply because they happen to be associated with a single > grace-period number? Or, to put it another way, suppose that same number > of memory blocks were distributed over a large number of grace-period > sequence numbers? How could this possibly cause an OOM to be more likely > than if the same nubmer of memory blocks were associated with a single > grace-period number? We just want a callback every time one of those grace periods expire, so the pending objects can be freed as soon as they're ready. This isn't _fatal_ for the kvfree_rcu() backend, since we have memory reclaim to fall back on, but it would still definitely be preferable for rcu_pending to be getting the notification from core RCU and avoid the more expensive memory reclaim path. It is more critical if we want to use this for a faster call_rcu() backend.
