On 2017-09-06 15:12:13 -0400, Tom Lane wrote: > Andres Freund <and...@anarazel.de> writes: > > On 2017-09-06 14:31:26 -0400, Tom Lane wrote: > >> However, if that's the reasoning, why don't we make all of these > >> use simple reads? It seems unlikely that a locked read is free. > > > We don't really use locked reads? All the _atomic_ wrapper forces is an > > actual read from memory rather than a register. > > It looks to me like two of the three implementations promise no such > thing.
They're volatile vars, so why not? > Even if they somehow do, it hardly matters given that the cmpxchg loop > would be self-correcting. Well, in this one instance maybe, hardly in others. > Mostly, though, I'm looking at the fallback pg_atomic_read_u64_impl > implementation (with a CAS), which seems far more expensive than can > be justified for this. What are you suggesting as an alternative? - Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
