On Mon, Jan 22, 2024 at 8:58 AM <reid.thomp...@crunchydata.com> wrote: > On Fri, 2024-01-19 at 17:37 -0500, reid.thomp...@crunchydata.com wrote: > > On Sat, 2024-01-13 at 10:31 -0700, Roberto Mello wrote: > > > > > > I can add a suggestion for the user to consider increasing > > > shared_buffers in accordance with higher max_connections, but it > > > would be better if there was a "rule of thumb" guideline to go > > > along. I'm open to suggestions. > > > > > > I can revise with a similar warning in max_prepared_xacts as well. > > > > > > Sincerely, > > > > > > Roberto > > > > Can a "close enough" rule of thumb be calculated from: > > postgresql.conf -> log_min_messages = debug3 > > > > start postgresql with varying max_connections to get > > CreateSharedMemoryAndSemaphores() sizes to generate a rough equation > > > > or maybe it would be sufficient to advise to set log_min_messages = > debug3 on a test DB and start/stop it with varying values of > max_connections and look at the differing values in > DEBUG: invoking IpcMemoryCreate(size=...) log messages for themselves. > >
I'm of the opinion that advice suggestingDBA's set things to DEBUG 3 is unfriendly at best. If you really want to add more, there is an existing unfriendly section of the docs at https://www.postgresql.org/docs/devel/kernel-resources.html#LINUX-MEMORY-OVERCOMMIT that mentions this problem, specifically: "If PostgreSQL itself is the cause of the system running out of memory, you can avoid the problem by changing your configuration. In some cases, it may help to lower memory-related configuration parameters, particularly shared_buffers, work_mem, and hash_mem_multiplier. In other cases, the problem may be caused by allowing too many connections to the database server itself. In many cases, it may be better to reduce max_connections and instead make use of external connection-pooling software." I couldn't really find a spot to add in your additional info, but maybe you can find a spot that fits? Or maybe a well written walk-through of this would make for a good wiki page in case people really want to dig in. In any case, I think Roberto's original language is an improvement over what we have now, so I'd probably recommend just going with that, along with a similar note to max_prepared_xacts, and optionally a pointer to the shared mem section of the docs. Robert Treat https://xzilla.net
