Re: Overhead cost of Serializable Snapshot Isolation

Dan Ports <drkp@csail.mit.edu> wrote:
> I spent some time thinking about this a while back, but didn't
> have time to get very far. The problem isn't contention in the
> predicate lock manager (which is partitioned) but the single lock
> protecting the active SerializableXact state.
> 
> It would probably help things a great deal if we could make that
> lock more fine-grained. However, it's tricky to do this without
> deadlocking because the serialization failure checks need to
> examine a node's neighbors in the dependency graph.
Did you ever see much contention on
SerializablePredicateLockListLock, or was it just
SerializableXactHashLock?  I think the former might be able to use
the non-blocking techniques, but I fear the main issue is with the
latter, which seems like a harder problem.
-Kevin