Thanks, for q2 - if work_mem is a limit before spilling onto disk, is there a min amount of memory which gets allocated to each session when it starts?
On Mon, Feb 10, 2020 at 3:51 AM Naresh g <naresh5...@gmail.com> wrote: > 1. Yes, by default it is advisable to set 25% of RAM to shared buffers > because community version postgres highly depends on OS cache, which means > when you fetch something from disk, it is first copied to OS cache (75%) > then to shared buffers(25%). > Two copies of data will be there in your system RAM. > The copy is called buffered IO. > > Amazon Aurora eliminates this buffered IO, hence it is not required you > stick to restrict 25% of RAM. > > 2. Work_mem is just setting, if you sort something out your session uses > than memory other wise it just lies at OS. > > On Mon, 10 Feb, 2020, 1:34 PM Ayub M, <hia...@gmail.com> wrote: > >> >> 1. shared_buffers - In a regular PostgreSQL installation, say I am >> allocating 25% of my memory to shared_buffers that means it leaves 75% for >> rest such as OS, page cache and work_mems etc. Is my understanding >> correct? >> If so, AWS Aurora for Postgres uses 75% of memory for shared_buffers, then >> it would leave just 25% for other things? >> 2. Does the memory specified for work_mem, fully gets allocated to >> all sessions irrespective of whether they do any sorting or hashing >> operations? >> >> >> -- >> Regards, >> Ayub >> > -- Regards, Ayub
