Hi Derrick, Thank you for your response. I saw this document and trying to understand "Interaction with the Operating System Cache" which is mentioned in this document.
I have the following question- Hows does the shared buffer in Postgres rely on the Operating System cache? Suppose my RAM is 8 GB and shared_buffer is 24 MB in postgres. And there are some dirty pages in shared_buffer and I need to write a dirty page back to the disk to bring in a new page. What happens in this case? The dirty page will be written to the disk considering the shared_buffer size as 24 MB? or it will not be written and will stay in RAM which is 8 GB? Thanks, Preetika On Fri, May 27, 2011 at 2:11 PM, Derrick Rice <derrick.r...@gmail.com>wrote: > Check out the "Inside the PostgreSQL Buffer Cache" link here: > > http://projects.2ndquadrant.com/talks > > Thanks to Greg Smith (active here). > > Derrick > > > On Fri, May 27, 2011 at 3:36 PM, preetika tyagi > <preetikaty...@gmail.com>wrote: > >> Hi All, >> >> I am little confused about the internal working of PostgreSQL. There is a >> parameter shared_buffer in postgres.conf and I am assuming that it is used >> for buffer management in PostgreSQL. If there is a need to bring in a new >> page in the buffer and size exceeds the shared_buffer limit, a victim dirty >> page will be written back to the disk. >> >> However, I have read on many links that PostgreSQL depends on the OS for >> caching. (http://www.varlena.com/GeneralBits/Tidbits/perf.html#shbuf) >> >> So my question is, the actual limit of the shared buffer will be defined >> by OS or the shared_buffer parameter in the postgres.conf to figure whether >> a victim dirty page needs to be selected for disk write or not? >> >> Thanks! >> > >
