[sysv 로 세팅]
[enterprisedb@ssd01:/opt/edb/as10/data]
$ psql
psql.bin (10.6.13)
Type "help" for help.
edb=# show dynamic_shared_memory_type ;
dynamic_shared_memory_type
----------------------------
sysv
(1 row)
edb=#
[root@ssd01:/dev/shm]
# ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x005311a1 720896 enterprise 600 56 8
0x548f5e8b 753665 enterprise 600 6928 8
0x408f4840 819203 enterprise 600 168 1
[root@ssd01:/dev/shm]
#
[root@ssd01:/dev/shm]
# ls -l /dev/shm/
total 0
[root@ssd01:/dev/shm]
#
[posix 로 세팅]
[enterprisedb@ssd01:/opt/edb/as10/data]
$ psql
psql.bin (10.6.13)
Type "help" for help.
edb=# show dynamic_shared_memory_type ;
dynamic_shared_memory_type
----------------------------
posix
(1 row)
edb=#
[root@ssd01:/dev/shm]
# ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x005311a1 851968 enterprise 600 56 8
[root@ssd01:/dev/shm]
#
[root@ssd01:/dev/shm]
# ls -l
total 12
-rw------- 1 enterprisedb enterprisedb 168 Dec 27 11:59 PostgreSQL.1642690918
-rw------- 1 enterprisedb enterprisedb 6928 Dec 27 11:59 PostgreSQL.303792158
[root@ssd01:/dev/shm]
#
-------------------
posix 로 할당해도 sysv 메모리를 일부 쓰는 이유는 아래에 나와있습니다.
18.4.1. Shared Memory and Semaphores
....
Upon starting the server, PostgreSQL normally allocates a very small amount of System V shared memory, as well as a much larger amount of POSIX (mmap) shared memory.
