RFR: 8203359: Container level resources events

[Severin Gehwolf]

On Thu, 25 Mar 2021 23:28:18 GMT, Erik Gahlin <egahlin at openjdk.org> wrote:

> Does each getter call result in parsing /proc, or do things aggregated over several calls or hooks?

>From the looks of it the event emitting code uses `Metrics.java` interface for retrieving the info. Each call to a method exposed by Metrics result in file IO on some cgroup (v1 or v2) interface file(s) in `/sys/fs/...`. I don't see any aggregation being done.

On the hotspot side, we implemented some caching for frequent calls (JDK-8232207, JDK-8227006), but we didn't do that yet for the Java side since there wasn't any need (so far). If calls are becoming frequent with this it should be reconsidered.

So +1 on getting some data on what the perf penalty of this is.

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PR: https://git.openjdk.java.net/jdk/pull/3126