Comparison
OvercommitvsResource limit
Overcommit
the sum of every limit on the node is three times the node, and it works fine until the day everything is busy at once.
Allowing the total of workloads' limits to exceed a node's real capacity, on the assumption that they will not all peak together. It is the mechanism that makes shared infrastructure economical, and it is a bet rather than a configuration. The bet loses in exactly the situation you care about — a correlated traffic spike — which is when eviction and throttling arrive together and the platform looks like it caused the incident.
Full entry →Resource limit
the container went one byte over its memory ceiling and the kernel killed it outright, mid-request.
The hard ceiling a container may consume, enforced by the kernel rather than by the scheduler. The two resources behave completely differently at the ceiling: CPU is throttled, so the workload gets slow, and memory is not compressible, so the process is killed. That asymmetry is why a CPU limit shows up as mysterious latency and a memory limit shows up as a restart loop.
Full entry →