Why the system was crashed with `Out of memory` even though memory usage is low?

Issue

• System was crashed with the below message.

Kernel panic - not syncing: Out of memory: system-wide panic_on_oom is enabled

• Before this, there was a message with memory details.

[7002168.880590] SysRq : Manual OOM execution
[7002168.880881] kworker/0:1 invoked oom-killer: gfp_mask=0xd0, order=0, oom_score_adj=0
[7002168.881238] kworker/0:1 cpuset=/ mems_allowed=0
[7002168.881455] CPU: 0 PID: 53863 Comm: kworker/0:1 Kdump: loaded Tainted: G        W  OE  ------------   3.10.0-1160.76.1.el7.x86_64 #1
...