Thanks Tom, that makes a lot of sense. Given we're seeing low iowait and blk_read_time at 4GB shared_buffers, sounds like we should just declare victory here and be happy with that setting?
On Wed, Dec 14, 2022 at 10:27 AM Tom Lane <t...@sss.pgh.pa.us> wrote: > Jordan Hurwich <jhurw...@pulsasensors.com> writes: > > I'm familiar with the article you linked to, and part of my surprise is > > that with these 32GB RAM machines we're seeing better performance at > 12.5% > > (4GB) than the commonly recommended 25% (8GB) of system memory for > > shared_buffers. Your notes about disk read stats from Postgres > potentially > > actually representing blocks read from the OS cache make sense, I just > > imagined that Postgres would be better at managing the memory when it was > > dedicated to it via shared_buffers than the OS (obviously with some point > > of diminishing returns); and I'm still hoping there's some Postgres > > configuration change we can make that enables better performance through > > improved utilization of shared_buffers at the commonly recommended 25% of > > system memory. > > Keep in mind that 25% was never some kind of golden number. It is > a rough rule of thumb that was invented for far smaller machines than > what you're talking about here. > > regards, tom lane >
