On Tue, Jul 09, 2024 at 07:36:41AM -0700, Paul E. McKenney wrote: > > Per VMA refcounts or per VMA locks are a complete fail IMO. > > Not even to allow concurrent updates of the address space by different > threads of a process? Well, I'm sure it helps some workloads. But for others it is just moving the problem. > For me, per-VMA locking's need to RCU-protect the VMA is a good step > towards permitting RCU-protected scans of the Maple Tree, which then > gets lockless lookup. Right, the question is if the VMA lock is required to be stable against splitting. If that is the case, we're hosed :/ At the time I added a seqcount for that, but I'm also remembering that's one of the things people complained about for single threaded performance.
