On Tue, 12 Mar 2024 07:59:12 GMT, Yi Yang <yy...@openjdk.org> wrote:
> We've received feedback from users of cloud APM platform wanting the new
> version of the JDK to allow the HotSpotDiagnosticMXBean.dumpHeap
> underpinnings to reduce STW time using sgemented heapdump. Supporting
> segmented heapdump for mxbean is a reasonable requirement and adds little
> additional complexity, both in terms of maintainability and understanding.
Hi!
Segmented is an awkward term as we use that word inside hprof too. For the
previous change we used the phrase "two phase" as well as calling it segmented,
which I think helps.
Also this change means jmm_DumpHeap will always use
HeapDumper::default_num_of_dump_threads().
That's not a bad thing, but could the bug title be something like "Enable
two-phase heap dump for HotSpotDiagnosticMXBean (JMX)" ? I think then it's
clearer what's happening just from the title.
+ if (current_thread->is_AttachListener_thread() || !_oome) {
I think "!_oome" here means "we are called from JMX" ? We should clarify. 8-)
Trying to suggest a way of describing this.
// Operating in attach listener or called by management library:
// perform heapdump file merge operation in the current thread, preventing
us
// from occupying the VM Thread, which in turn affects the occurrence of
// GC and other VM operations.
So the other case is only HeapDumpOnOutOfMemoryError processing, where we do
the merge in a VM operation? Just checking if that's all agreed. 8-)
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PR Review: https://git.openjdk.org/jdk/pull/18221#pullrequestreview-1935100384
