At Wed, 24 May 2023 09:57:35 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in
> dynamic_shared_memory_type. Outside of Windows, it first prefers
> posix, then sysv and finally mmap. Thus it is quite usual to use posix
> for DSM segments. Actually posix is defaultly used for
It is written in the documentation.
https://www.postgresql.org/docs/15/runtime-config-resource.html#GUC-DYNAMIC-SHARED-MEMORY-TYPE
> The use of the mmap option, which is not the default on any
> platform, is generally discouraged because the operating system may
> write modified pages back to disk repeatedly, increasing system I/O
> load; however, it may be useful for debugging, when the pg_dynshmem
> directory is stored on a RAM disk, or when other shared memory
> facilities are not available.
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center
