Docker container high memory usage: how to diagnose it

Mon, 01 Jan 0001 00:00:00 +0000

Your container is sitting at 90% of its memory limit but has not been OOMKilled. Or it is being killed repeatedly and you cannot tell whether the limit is too low or the application is leaking. docker stats shows a single percentage, but that number does not reveal the breakdown between reclaimable page cache and anonymous memory that the kernel cannot reclaim. To diagnose this correctly, you need to decompose cgroup memory.stat, map it to your runtime’s actual allocations, and decide whether the problem is cache pressure, a runtime mismatch, or a true leak.

Docker memory usage explained: anonymous, file, slab, and what counts

Mon, 01 Jan 0001 00:00:00 +0000

You look at docker stats, see a container sitting at 1.2 GB of a 1.5 GB limit, and assume it is about to explode. It might be fine. That total includes page cache the kernel will reclaim the second another process asks for memory. Meanwhile, a different container reports 600 MB with no limit set, yet its anonymous memory grows 50 MB per hour and will force a host-level OOM kill before lunch.

Memory Usage on Netdata

Docker container high memory usage: how to diagnose it

Docker memory usage explained: anonymous, file, slab, and what counts