Centos not using available memory - postgresql

Question

I have Centos installed on a server with 64gb memory and it seems as if the memory usage is being suppressed.
I came to this conclusion by running an insert statement where I insert 10million rows into a Postgres table in both a Timescaledb and a standard Postgres instance hosted on Docker.
I monitored the insert process in three different ways:
Docker stats timescaledb:
CONTAINER CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS
timescaledb 73.14% 10.42 MiB / 62.75 GiB 0.02% 8.46 kB / 8.39 kB 0 B / 15.1 GB 12
free -i gives the following:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
16298 avahi 20 0 16.2g 762356 759908 R 41.5 1.2 0:22.72 postgres
16127 avahi 20 0 16.2g 693080 691968 S 4.3 1.1 0:01.29 postgres
16129 avahi 20 0 16.2g 17748 16712 S 2.3 0.0 0:00.87 postgres
1578 root 30 10 1232780 86976 11568 S 0.7 0.1 0:46.34 osqueryd
17014 root 20 0 162264 2480 1596 R 0.7 0.0 0:00.03 top
928 root 20 0 90608 3212 2352 S 0.3 0.0 0:03.47 rngd
16128 avahi 20 0 16.2g 132064 131016 S 0.3 0.2 0:00.18 postgres
free -h gives the following
total used free shared buff/cache available
Mem: 62G 1.0G 58G 1.1G 3.1G 56G
Swap: 62G 0B 62G
I know that Timescaledb is an extension of Postgres which comes with its own memory configurations, but the Docker container of Timescaledb configures these automatically for you (for instance effective cache size is set at 48gb as opposed to the default 4gb that Postgres ships with). I also ran a similar process with Apache spark with 16gb assigned to the worker and it ran into an oom error. Additionally, I did a similar test on a different smaller VM and the memory usage increased as expected. All of this leads me to believe that it's a Centos config setting that I am missing somewhere, and nothing to do with Timescale/Postgres?
I have added the following parameters to vm.overcommit_memory = 2 and vm.overcommit_ratio = 95 in /etc/sysctl.conf and ran sysctl -p to implement the settings, but this didn't make a difference.
kernel.shmall = 8224280
kernel.shmmax = 33686650880
kernel.shmmni = 4096
vm.overcommit_memory = 2
vm.overcommit_ratio = 95
Below is the output from cat /proc/meminfo
MemTotal: 65794240 kB
MemFree: 61098656 kB
MemAvailable: 59252660 kB
Buffers: 2120 kB
Cached: 3467144 kB
SwapCached: 0 kB
Active: 2817620 kB
Inactive: 884816 kB
Active(anon): 1109220 kB
Inactive(anon): 234708 kB
Active(file): 1708400 kB
Inactive(file): 650108 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 65535996 kB
SwapFree: 65535996 kB
Dirty: 88 kB
Writeback: 0 kB
AnonPages: 233188 kB
Mapped: 1175120 kB
Shmem: 1110756 kB
Slab: 204044 kB
SReclaimable: 142700 kB
SUnreclaim: 61344 kB
KernelStack: 7232 kB
PageTables: 14672 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 128040524 kB
Committed_AS: 18709300 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 408824 kB
VmallocChunk: 34325399548 kB
Percpu: 9216 kB
HardwareCorrupted: 0 kB
AnonHugePages: 96256 kB
CmaTotal: 0 kB
CmaFree: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 133604 kB
DirectMap2M: 66965504 kB
Is there maybe something I can try to increase my memory usage? Is there maybe a config setting that I am missing somehere?
Thanks in advance for any help

Answer 1

PostgreSQL also uses "unused" memory, because it uses buffered I/O. So this "unused memory" is used by the kernel to cache files – in the case of a database server, these will be database files. That way, I/O requests by PostgreSQL can be served from the kernel cache rather than causing disk I/O requests.