performance

The question that reveals whether someone knows what load average actually counts on Linux. It is not a CPU metric, and that single fact resolves the whole thing.

The swap-used graph is the least informative memory metric on the box. Here is what swappiness actually weights, which numbers to watch instead, and the policy worth defending.

One CPU doing all the packet work is a topology failure, not a tuning mystery. RSS queues, MSI-X vectors, local_cpulist and irqbalance: the whole chain from symptom to pin.

Loss-based versus model-based congestion avoidance decides whether your WAN transfers fill the pipe or die on the first stray drop. Here is the operator's decision, not the RFC summary.

Absolute caps versus latency-target protection, systemd IO attributes versus raw io.max, and why ionice lies to you. The staff-level answer assigns the job its own slice with intent.

Four-hour applies with throttling errors share one root cause more often than not. Diagnose which calls burn the quota, split the state along dependency seams, and touch the parallelism flag last, not first.

Compare the configured Service datapaths and their lookup and update mechanisms. The iptables datapath degrades with service count, and eBPF replaces a linear scan with a map lookup.

Tracing tells you which service and which span. It stops at the function boundary, and that is exactly where a CPU regression lives. Continuous profiling is the layer most teams do not have when they need it.

One saturated core on a proxy is rarely about raw traffic volume. It is a parallelism failure with three usual suspects, and the per-thread view names the culprit in minutes.

The box looks CPU-starved but the CPUs are starving themselves. Reading the reclaim loop correctly separates people who have sat on the console from people who have read about it.

Use shared evidence and an agreed experiment to resolve a cross-team production problem, while containing impact and escalating time-sensitive risk.