Manfred Spraul <[EMAIL PROTECTED]> writes: > Tom Lane wrote: >> The bigger problem here is that the SMP locking bottlenecks we are >> currently seeing are *hardware* issues (AFAICT anyway). The only way >> that futexes can offer a performance win is if they have a smarter way >> of executing the basic atomic-test-and-set sequence than we do; >> > lwlocks operations are not a basic atomic-test-and-set sequence. They > are spinlock, several nonatomic operations, spin_unlock.
Right, and it is the spinlock that is the problem. See discussions a few months back: at least on Intel SMP machines, most of the problem seems to have to do with trading the spinlock's cache line back and forth between CPUs. It's difficult to see how a futex is going to avoid that. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly