On Tue, Jan 21, 2020 at 11:12:06PM +0100, Mateusz Guzik wrote: > > This does not happen with rb trees and would not happen with the hash > table if there was bucket locking instead of per-cpu. > > I would stick to hash tables since they are easier to scale (both with > and without locks). > > For instance if 2 threads look up "/bin" and "/usr" and there is no > hash collision, they lock *separate* buckets and suffer less in terms > of cacheline bouncing. In comparison with rb trees they will take the > same lock. Of course this similarly does not scale if they are looking > up the same path.
I think there's probably a generic bucket-locked hashtable implementation in one of the code contributions Coyote Point made long ago. That said, we're talking about a screenful of code, so it's not like it'd be hard to rewrite, either. Do we want such a thing? Or do we want to press on towards more modern "that didn't work, try again" approaches like pserialize or the COW scheme you describe? -- Thor Lancelot Simon t...@panix.com "Whether or not there's hope for change is not the question. If you want to be a free person, you don't stand up for human rights because it will work, but because it is right." --Andrei Sakharov
