In our environment, OS cache is much bigger than postgres buffers. Postgres buffers around 8 GB, OS cache more than 100 GB. Maybe we should inspect pgfincore
On Wed, Sep 6, 2017 at 9:13 PM, Gerardo Herzig <gher...@fmed.uba.ar> wrote: > > > ----- Mensaje original ----- > > De: "Soni M" <diptat...@gmail.com> > > Para: pgsql-performance@postgresql.org > > Enviados: Miércoles, 6 de Septiembre 2017 5:12:26 > > Asunto: [PERFORM] OS cache management > > > > Hello All, I would like to know about how OS cache works for postgres > table > > and index file. > > > > Let's say I have 10 year data, and commonly used data only the last 1 > year. > > This data is quite big, so each table and index file is divided into > > several file in PGDATA/base > > > > Let's say 1 index named order_by_date has relfilenode = 1870772348, and > > it's file consist of 1870772348, 1870772348.1, and 1870772348.2 > > > > And for oftenly queried 1 year data, do ALL files for the order_by_date > > pushed to OS cache ? or it's just 1 file that contains index to this 1 > year > > data. > > > > Postgres has its own cache (defined by the "shared_buffers" variable). > Usually, the unit of movement in and out from the cache is a 8k page > (defined at compilation time), so you cant put it directly in terms of > files. > > There is an extension that can inspect the cache contents: > https://www.postgresql.org/docs/current/static/pgbuffercache.html > > HTH > Gerardo > -- Regards, Soni Maula Harriz
