memory

Most of what looks like used memory on a healthy Linux box is page cache doing its job. Knowing which column to read, and why df and du disagree, is half of Linux triage.

The scripting round in disguise. The constraint is the question: it exists to see whether you stream or whether you load, and everything else is about whether the script is safe to run twice.

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.

SIGKILL writes no stack trace and the application cannot defend itself. The verdict is already sitting in the kernel ring buffer, and reading it precisely is the skill being priced.

Transparent versus explicit hugepages is a control question, not a size question. Fork-heavy stores suffer THP copy-on-write amplification while large-resident databases gain TLB reach.

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.

The kill was not random and it was not fair. Learn the scoring function the kernel actually uses, then bend it with oom_score_adj before your monitoring dies during the next leak.

Spikes that march in step with BGSAVE are a page-size story, not a network story. Check actual huge-page usage, fork duration and copy-on-write pressure on the deployed kernel.

The heap is the part you configured and the smaller part of what the process uses. The kernel counts everything the cgroup touches, including the page cache the JVM never asked for.