Increase default effective_io_concurrency to 16 The default effective_io_concurrency has been 1 since it was introduced in b7b8f0b6096d2ab6e. Referencing the associated discussion [1], it seems 1 was chosen as a conservative value that seemed unlikely to cause regressions.
Experimentation on high latency cloud storage as well as fast, local nvme storage (see Discussion link) shows that even slightly higher values improve query timings substantially. 1 actually performs worse than 0 [2]. With effective_io_concurrency 1, we are not prefetching enough to avoid I/O stalls, but we are issuing extra syscalls. The new default is 16, which should be more appropriate for common hardware while still avoiding flooding low IOPs devices with I/O requests. [1] https://www.postgresql.org/message-id/flat/FDDBA24E-FF4D-4654-BA75-692B3BA71B97%40enterprisedb.com [2] https://www.postgresql.org/message-id/CAAKRu_Zv08Cic%3DqdCfzrQabpEXGrd9Z9UOW5svEVkCM6%3DFXA9g%40mail.gmail.com Reviewed-by: Andres Freund <and...@anarazel.de> Discussion: https://postgr.es/m/CAAKRu_Z%2BJa-mwXebOoOERMMUMvJeRhzTjad4dSThxG0JLXESxw%40mail.gmail.com Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/ff79b5b2aba02d720f9b7fff644dd50ce07b8c6e Modified Files -------------- doc/src/sgml/config.sgml | 38 +++++++++++---------------- src/backend/utils/misc/postgresql.conf.sample | 2 +- src/include/storage/bufmgr.h | 2 +- 3 files changed, 18 insertions(+), 24 deletions(-)
