On Mon, Jan 9, 2017 at 4:27 PM, Jonathon Nelson <jdnel...@dyn.com> wrote: > [I have not done a rigid analysis, here, but...] > > I *think* libpq is the culprit here. > > walsender says "Hey, libpq - please send (up to) 128KB of data!" and doesn't > "return" until it's "sent". Then it sends more. Regardless of the > underlying cause (nagle, tcp congestion control algorithms, umpteen > different combos of hardware and settings, etc..) in almost every test I saw > improvement (usually quite a bit). This was most easily observable with high > bandwidth-delay product links, but my time in the lab is somewhat limited.
This seems plausible to me. If it takes X amount of time for the upper layers to put Y amount of data into libpq's buffers, that imposes some limit on overall throughput. I mean, is it not sufficient to know that the performance improvement is happening? If it's happening, there's an explanation for why it's happening. It would be good if somebody else could try to reproduce these results, though. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
