On 19 September 2018 at 22:12, Kaixi Luo <kaixiluo@xxxxxxxxx> wrote: > Does a large shared_buffers impact checkpoint performance negatively? I was > under the impression that everything inside shared_buffers must be written > during a checkpoint. Only the dirty buffers get written. Also having too small a shared buffers can mean that buffers must be written more than they'd otherwise need to be. If a buffer must be evicted from shared buffers to make way for a new buffer then the chances of having to evict a dirty buffer increases with smaller shared buffers. Obviously, this dirty buffer needs to be written out before the new buffer can be loaded in. In a worst-case scenario, a backend performing a query would have to do this. pg_stat_bgwriter is your friend. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
