PostgreSQL启动报错“could not map anonymous shared memory: Cannot allocate memory”
基础信息
OS版本：Red Hat Enterprise Linux Server release 7.9 (Maipo)
DB版本：16.2
pg软件目录：/home/pg16/soft
pg数据目录：/home/pg16/data
端口：5777
报错
[pg16@test ~]$ pg_ctl start
waiting for server to start....2024-06-01 22:20:02.156 PDT [68668] DEBUG: registering background worker "logical replication launcher"
2024-06-01 22:20:02.157 PDT [68668] DEBUG: loaded library "pg_stat_statements"
2024-06-01 22:20:02.157 PDT [68668] FATAL: could not map anonymous shared memory: Cannot allocate memory
2024-06-01 22:20:02.157 PDT [68668] HINT: This error usually means that PostgreSQL's request for a shared memory segment exceeded available memory, swap space, or huge pages. To reduce the request size (currently 295698432 bytes), reduce PostgreSQL's shared memory usage, perhaps by reducing shared_buffers or max_connections.
2024-06-01 22:20:02.157 PDT [68668] LOG: database system is shut down
stopped waiting
pg_ctl: could not start server
Examine the log output.
PostgreSQL 请求的共享内存段超出了当前可用的内存、交换空间或大页内存 (huge pages)。当前请求的内存大小为 295,698,432 字节（约 282 MB）。
分析记录
[pg16@test ~]$ cat data/postgresql.conf |grep shared
shared_buffers = 256MB # min 128kB
#shared_memory_type = mmap # the default is the first option
dynamic_shared_memory_type = posix # the default is usually the first option
#min_dynamic_shared_memory = 0MB # (change requires restart)
#wal_buffers = -1 # min 32kB, -1 sets based on shared_buffers
shared_preload_libraries = 'pg_stat_kcache,pg_stat_statements,auto_explain' # (change requires restart)
[pg16@test ~]$ cat /proc/meminfo |grep Huge
AnonHugePages: 942080 kB
HugePages_Total: 150
HugePages_Free: 7
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
发现空闲的大页只有7个，不满足pg的启动需求，故报错。最终发现是其它数据库进程占用了，停了之后pg可以正常启动。
解决
[pg16@test log]$ pg_ctl start
waiting for server to start....2024-06-02 06:43:45.043 PDT [3636] DEBUG: registering background worker "logical replication launcher"
2024-06-02 06:43:45.043 PDT [3636] DEBUG: loaded library "pg_stat_statements"
2024-06-02 06:43:45.051 PDT [3636] LOG: redirecting log output to logging collector process
2024-06-02 06:43:45.051 PDT [3636] HINT: Future log output will appear in directory "log".
done
server started
谨记：心存敬畏，行有所止。