This commit makes our default random_page_cost = 4 out of line with these new settings (assumes modern SSD/NAS/SAN hardware) and more out of line with reality.
--------------------------------------------------------------------------- On Tue, Mar 18, 2025 at 01:08:47PM +0000, Melanie Plageman wrote: > Increase default maintenance_io_concurrency to 16 > > Since its introduction in fc34b0d9de27a, the default > maintenance_io_concurrency has been larger than the default > effective_io_concurrency. maintenance_io_concurrency primarily > controlled prefetching done on behalf of the whole system, for > operations like recovery. Therefore it makes sense for it to have a > value equal to or greater than effective_io_concurrency, which controls > I/O concurrency for reading a relation in a bitmap heap scan. > > ff79b5b2ab increased effective_io_concurrency to 16, so we'll increase > maintenance_io_concurrency as well. For now, though, we'll keep the > defaults of effective_io_concurrency and maintenance_io_concurrency > equal to one another (16). > > On fast, high IOPs systems, significantly higher values of > maintenance_io_concurrency are observably beneficial [1]. However, such > values would flood low IOPs systems and increase overall system I/O > latency. > > It is worth mentioning that since 9256822608f and c3e775e608f, > maintenance_io_concurrency also controls the I/O concurrency of each > vacuum worker. Since many autovacuum workers may be simultaneously > issuing I/Os, we want to keep maintenance_io_concurrency appropriately > conservative. > > [1] > https://postgr.es/m/c5d52837-6256-0556-ac8c-d6d3d558820a%40enterprisedb.com > > Suggested-by: Jakub Wartak <jakub.war...@enterprisedb.com> > Discussion: > https://postgr.es/m/CAKZiRmxdHQaU%2B2Zpe6d%3Dx%3D0vigJ1sfWwwVYLJAf%3Dud_wQ_VcUw%40mail.gmail.com > > Branch > ------ > master > > Details > ------- > https://git.postgresql.org/pg/commitdiff/cc6be07ebde2aef7cc0507f997f563ce77c00a00 > > Modified Files > -------------- > doc/src/sgml/config.sgml | 8 ++++---- > src/backend/utils/misc/postgresql.conf.sample | 2 +- > src/include/storage/bufmgr.h | 2 +- > 3 files changed, 6 insertions(+), 6 deletions(-) > -- Bruce Momjian <br...@momjian.us> https://momjian.us EDB https://enterprisedb.com Do not let urgent matters crowd out time for investment in the future.
