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8329605: hs errfile generic events - move memory protections and nmethod flushes to separate sections #18626

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@MBaesken MBaesken commented Apr 4, 2024

Currently the 'generic' hs_errfile Events message log (filled by Events::log) is sometimes rather full by messages for memory protection operations and nmethod flushes. Those seem to occur quite often and potentially move out other less frequent events, because the number of entries in the log is limited.
It might be better to separate the events into separate sections.

The mentioned memory protection operations related entries look like this :
Event: 0.178 Protecting memory [0x000000016ebf0000,0x000000016ebfc000] with protection modes 0


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  • JDK-8329605: hs errfile generic events - move memory protections and nmethod flushes to separate sections (Enhancement - P4)

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👋 Welcome back mbaesken! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

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@MBaesken This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8329605: hs errfile generic events - move memory protections and nmethod flushes to separate sections

Reviewed-by: lucy, stefank, stuefe

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At the time when this comment was updated there had been 141 new commits pushed to the master branch:

  • 77a217d: 8330095: RISC-V: Remove obsolete vandn_vi instruction
  • 717a07b: 8322140: javax/swing/JTable/JTableScrollPrintTest.java does not print the rows and columns of the table in Nimbus and Aqua LookAndFeel
  • aebfd53: 8329660: G1: Improve TestGCLogMessages to be more precise
  • 006a516: 8329962: Remove CardTable::invalidate
  • c7fcd62: 8330006: Serial: Extract out ContiguousSpace::block_start_const
  • 2c8b432: 8330003: Serial: Move the logic of FastEvacuateFollowersClosure to SerialHeap
  • 2c45eca: 8328879: G1: Some gtests modify global state crashing the JVM during GC after JDK-8289822
  • bde3fc0: 8330106: C2: VectorInsertNode::make() shouldn't call ConINode::make() directly
  • e45fea5: 8329757: Crash with fatal error: DEBUG MESSAGE: Fast Unlock lock on stack
  • ece7d43: 8329416: Split relocation pointer map into read-write and read-only maps
  • ... and 131 more: https://git.openjdk.org/jdk/compare/bea493bcb86370dc3fb00d86c545f01fc614e000...master

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stefank commented Apr 4, 2024

We still have flooding in the frequent events. Instead of creating a common section for these vent, did you consider creating two new separate, specific sections for memory protection and nmethod flushing?

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MBaesken commented Apr 4, 2024

We still have flooding in the frequent events. Instead of creating a common section for these vent, did you consider creating two new separate, specific sections for memory protection and nmethod flushing?

I thought about creating new specific sections. Regarding those 2, maybe they are a bit too specific ? But on the other hand, if others like this idea, I am fine with it (creating sections for memory protection operations and for nmethod flushing).

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MBaesken commented Apr 8, 2024

But on the other hand, if others like this idea, I am fine with it (creating sections for memory protection operations and for nmethod flushing).

I asked around in my team and added a separate section for the nmethod flush operations.

@@ -97,6 +99,8 @@ void Events::print() {
void Events::init() {
if (LogEvents) {
_messages = new StringEventLog("Events", "events");
_nmethod_flush_messages = new StringEventLog("Nmethod flushs", "nmethodflushs");
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Should be "flushes" or "flushing events".

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LGTM - given the scope of this PR.
In general, I don't like the event log to be split into multiple streams being printed separately. Yes, separate sections prevent displacement of events by other, too verbose, events. On the other hand, time coherence is lost or has to be manually re-established by the support engineer. Often enough, an issue can only be understood when seeing multiple/all events in timely order.

Merging the event sections at print time by timestamp would be a helpful enhancement.

@openjdk openjdk bot added the ready Pull request is ready to be integrated label Apr 9, 2024
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stefank commented Apr 10, 2024

LGTM - given the scope of this PR. In general, I don't like the event log to be split into multiple streams being printed separately. Yes, separate sections prevent displacement of events by other, too verbose, events. On the other hand, time coherence is lost or has to be manually re-established by the support engineer. Often enough, an issue can only be understood when seeing multiple/all events in timely order.

Merging the event sections at print time by timestamp would be a helpful enhancement.

FWIW, I think I am of the opposite opinion. I find it very helpful to have the events separated into distinct sections and wouldn't want them all combined into one big section.

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Hi Lucy, thanks for the review ! May I have a second one please ?

FWIW, I think I am of the opposite opinion. I find it very helpful to have the events separated into distinct sections and wouldn't
want them all combined into one big section.

Yeah, both approaches (one single big log, or multiple ones) have pros and cons.
But having multiple logs is a long established HS approach so I do not think that it is in scope of this PR to change the established approach.

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... I do not think that it is in scope of this PR ...
Oh no, I didn't want to suggest to do such a change in the scope of this PR. And yes, I agree, there are reasons why you would want separate streams. As always, a solution that suits all needs is hard to find.

@openjdk openjdk bot changed the title JDK-8329605: hs errfile generic events - introduce sections for Frequent/NotFrequent Events 8329605: hs errfile generic events - introduce sections for Frequent/NotFrequent Events Apr 10, 2024
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I think it's ok if @stefank also likes it.

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tstuefe commented Apr 11, 2024

Hmm, I think the separation makes sense, but I don't like the "frequent" moniker. All other event logs are separated by thematic area. "frequent" is orthogonal to that. I can have frequent/non-frequent class loading messages, or exceptions.

My proposal would be either to drop these memory protection events (do we need them? or are they remnants of some old support issues?) or to put them into a 'memprot' section or similar.

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stefank commented Apr 11, 2024

I agree with @tstuefe

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MBaesken commented Apr 12, 2024

My proposal would be either to drop these memory protection events (do we need them? or are they remnants of some old >support issues?) or to put them into a 'memprot' section or similar.

A separate memprotect section would be good I can add this.
I think usually these protection events appear around/after threads are added. I think we had some issues with these mem protections in the past so I would be cautious to completely remove them.

@MBaesken MBaesken changed the title 8329605: hs errfile generic events - introduce sections for Frequent/NotFrequent Events 8329605: hs errfile generic events - move memory protections and nmethod flushes to separate sections Apr 12, 2024
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I added a memprotect section.

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Hi Stefan, thanks for the review !

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Good, thank you

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/integrate

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openjdk bot commented Apr 12, 2024

Going to push as commit 397d948.
Since your change was applied there have been 145 commits pushed to the master branch:

  • f706949: 8329781: Serial: Remove serialFullGC.inline.hpp
  • 0f78d01: 8329658: Serial: Refactor ContiguousSpace::_next_compaction_space
  • b8f675f: 8329771: G1: Refactor G1BlockOffsetTable::verify
  • 3e9c381: 8329488: Move OopStorage code from safepoint cleanup and remove safepoint cleanup code
  • 77a217d: 8330095: RISC-V: Remove obsolete vandn_vi instruction
  • 717a07b: 8322140: javax/swing/JTable/JTableScrollPrintTest.java does not print the rows and columns of the table in Nimbus and Aqua LookAndFeel
  • aebfd53: 8329660: G1: Improve TestGCLogMessages to be more precise
  • 006a516: 8329962: Remove CardTable::invalidate
  • c7fcd62: 8330006: Serial: Extract out ContiguousSpace::block_start_const
  • 2c8b432: 8330003: Serial: Move the logic of FastEvacuateFollowersClosure to SerialHeap
  • ... and 135 more: https://git.openjdk.org/jdk/compare/bea493bcb86370dc3fb00d86c545f01fc614e000...master

Your commit was automatically rebased without conflicts.

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@MBaesken Pushed as commit 397d948.

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