PostgreSQL 10 High Performance - Third Edition

commit_delay and commit_siblings

Before synchronous_commit was implemented, there was an earlier attempt to add the same sort of feature enabled by the commit_delay and commit_siblings parameters. These are not effective parameters to tune in most cases. It is extremely difficult to show any speedup by adjusting them, and quite easy to slow every transaction down by tweaking them. The only case where they have shown some value is for extremely high I/O rate systems. Increasing the delay to a very small amount can make writes happen in bigger blocks, which sometimes turn out better aligned when combined with larger RAID stripe sizes in, particular.