On 10/06/15 16:20, Andres Freund wrote: > That's precisely what I referred to in the bit you cut away...
I apologize, yes. On 10/06/15 16:25, Tom Lane wrote: > Optimizing for misuse of the mechanism is not the way. I absolutely agree and I really appreciate all efforts towards lockless data structures or at least better concurrency using classical mutual exclusion. But still I am convinced that on today's massively parallel NUMAs, spinlocks are plain wrong: - Even if critical sections are kept minimal, they can still become hot spots - When they do, we get potentially massive negative scalability, it will be hard to exclude the possibility of a system "tilting" under (potentially yet unknown) load patterns as long as userland slocks exist. Briefly: When slocks fail, they fail big time - slocks optimize for the best case, but I think on today's systems we should optimize for the worst case. - The fact that well behaved mutexes have a higher initial cost could even motivate good use of them rather than optimize misuse. Cheers, Nils -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
