On Tue, Nov 21, 2023 at 05:03:00PM +0100, Peter Zijlstra wrote: > On Tue, Nov 21, 2023 at 07:58:40AM -0800, Paul E. McKenney wrote: > > > Tasks Trace RCU allows general blocking in its readers, not just the > > subject-to-priority-boosting blocking permitted within preemptible RCU > > readers. Restrictions on the use of Tasks Trace RCU are in place to allow > > getting away with this general blocking. Even systems generously endowed > > with memory are not going to do well when the RCU grace period is blocked > > on I/O, especially if that I/O is across a network to a slow file server. > > > > Which means a separate RCU instance is needed. Which is Tasks Trace RCU. > > Separate instance not a problem, nor really the question. > > What is the basic mechanism of task-tracing? Is it really the existing > tasks-rcu extended with read-side critical sections and call_rcu ? > > If so, then why not have it be tasks-rcu? > > Or is it a variant of the preemptible/SRCU class of RCUs that are > counter-array based? I suspect not. > > So once again, what exactly is tasks-tracing ? I think we covered this elsewhere in the thread, but if there are lingering questions, you know where to find us. ;-) Thanx, Paul
