jmx-dev RFR: 8304074: [JMX] Add an approximation of total bytes allocated on the Java heap by the JVM [v5]

[Volker Simonis]

On Mon, 8 May 2023 02:10:48 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Paul Hohensee has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   8304074: [JMX] Add an approximation of total bytes allocated on the Java heap by the JVM
>
> src/hotspot/share/services/management.cpp line 2107:
> 
>> 2105:     // when result is initialized.
>> 2106:     jlong result = ThreadService::exited_allocated_bytes();
>> 2107:     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next();) {
> 
> If you call `exited_allocated_bytes` whilst you have an active `ThreadsListHandle` then you at least ensure you don't miss accounting for threads that are just about to terminate.

Do you mean something like:

    JavaThreadIteratorWithHandle jtiwh;
    jlong result = ThreadService::exited_allocated_bytes();
    while (JavaThread *thread = jtiwh.next()) {
      ...

That would be fine for me. Otherwise I agree with the current compromise between accuracy and speed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13814#discussion_r1187488276