From 336497ae1df22b966c3b05826987eb3b374f551a Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Wed, 21 Jul 2021 16:40:43 -0700 Subject: [PATCH] pgbench: When using pipelining only do PQconsumeInput() when necessary. Up to now we did a PQconsumeInput() for each pipelined query, asking the OS for more input - which it often won't have, as all results might already have been sent. That turns out to have a noticeable performance impact. Alvaro Herrera reviewed the idea to add the PQisBusy() check, but not this concrete patch. Author: Andres Freund Discussion: https://postgr.es/m/20210720180039.23rivhdft3l4mayn@alap3.anarazel.de Backpatch: 14, where libpq/pgbench pipelining was introduced. --- src/bin/pgbench/pgbench.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c index 364b5a2e47d..129cf2ed61d 100644 --- a/src/bin/pgbench/pgbench.c +++ b/src/bin/pgbench/pgbench.c @@ -3460,7 +3460,14 @@ advanceConnectionState(TState *thread, CState *st, StatsData *agg) */ case CSTATE_WAIT_RESULT: pg_log_debug("client %d receiving", st->id); - if (!PQconsumeInput(st->con)) + + /* + * Only check for new network data if we processed all data + * fetched prior. Otherwise we end up doing a syscall for each + * individual pipelined query, which has a measurable + * performance impact. + */ + if (PQisBusy(st->con) && !PQconsumeInput(st->con)) { /* there's something wrong */ commandFailed(st, "SQL", "perhaps the backend died while processing"); -- 2.32.0.rc2