Re: MIT benchmarks pgsql multicore (up to 48)performance

On Mon, Oct 04, 2010 at 01:13:36PM -0400, Robert Haas wrote:
> I believe the "one of only 16 global mutexes" comment is referring to
> NUM_LOCK_PARTITIONS (there's also NUM_BUFFER_PARTITIONS, but that
> wouldn't be relevant for row and table-level locks).

Yes -- my understanding is that they hit two lock-related problems: 1) LWLock contention caused by acquiring the same
lockin compatible    modes (e.g. multiple shared locks) 2) false contention caused by acquiring two locks that hashed
tothe    same partition
 
and the first was the worse problem. The lock-free structures helpe
with both, so the impact of changing NUM_LOCK_PARTITIONS was less
interesting.

Dan

-- 
Dan R. K. Ports              MIT CSAIL                http://drkp.net/