8277397: ZGC: Add JFR event for temporary latency measurements #6454

stefank · 2021-11-18T13:09:59Z

I often measure latencies and stalls using JFR events. I'd like to add an event that can be used for these ad-hoc measurements during development and debugging.

Progress

Change must not contain extraneous whitespace
Commit message must refer to an issue
Change must be properly reviewed

Issue

JDK-8277397: ZGC: Add JFR event for temporary latency measurements

Reviewers

Erik Österlund (@fisk - Reviewer)
Jaroslav Bachorik (@jbachorik - Reviewer)
Per Liden (@pliden - Reviewer)
Markus Grönlund (@mgronlun - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/6454/head:pull/6454
$ git checkout pull/6454

Update a local copy of the PR:
$ git checkout pull/6454
$ git pull https://git.openjdk.java.net/jdk pull/6454/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 6454

View PR using the GUI difftool:
$ git pr show -t 6454

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/6454.diff

stefank · 2021-11-18T13:10:07Z

/label hotspot-gc jfr

bridgekeeper · 2021-11-18T13:10:46Z

👋 Welcome back stefank! 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.

openjdk · 2021-11-18T13:12:35Z

@stefank The label jfr is not a valid label. These labels are valid:

serviceability
hotspot
hotspot-compiler
ide-support
kulla
i18n
shenandoah
jdk
javadoc
security
hotspot-runtime
jmx
build
nio
client
core-libs
compiler
net
hotspot-gc
hotspot-jfr

openjdk · 2021-11-18T13:13:18Z

@stefank The following label will be automatically applied to this pull request:

hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

mlbridge · 2021-11-18T13:16:53Z

Webrevs

stefank · 2021-11-18T13:18:04Z

/label hotspot-gc hotspot-jfr

openjdk · 2021-11-18T13:19:39Z

@stefank
The hotspot-gc label was successfully added.

The hotspot-jfr label was successfully added.

stefank · 2021-11-18T13:32:48Z

/label remove hotspot

openjdk · 2021-11-18T13:33:27Z

@stefank
The hotspot label was successfully removed.

stefank · 2021-11-18T13:33:48Z

Retrying with correct labels.

fisk

Looks good.

openjdk · 2021-11-18T14:23:58Z

@stefank 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:

8277397: ZGC: Add JFR event for temporary latency measurements

Reviewed-by: eosterlund, jbachorik, pliden, mgronlun

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 79 new commits pushed to the master branch:

32839ba: 8266593: vmTestbase/nsk/jvmti/PopFrame/popframe011 fails with "assert(java_thread == _state->get_thread()) failed: Must be"
8051041: 8277534: Remove unused ReferenceProcessor::has_discovered_references
3f847fe: 8277385: Zero: Enable CompactStrings support
ca31ed5: 8275448: [REDO] AArch64: Implement string_compare intrinsic in SVE
4ff4301: 8224922: Access JavaFileObject from Element(s)
0a9e76c: 8277485: Zero: Fix fast{i,f}access_0 bytecodes handling
1c215f3: 8272773: Configurable card table card size
1d7cef3: 8276662: Scalability bottleneck in SymbolTable::lookup_common()
c79a485: 8277494: [BACKOUT] JDK-8276150 Quarantined jpackage apps are labeled as "damaged"
2ab43ec: 8273544: Increase test coverage for snippets
... and 69 more: https://git.openjdk.java.net/jdk/compare/9a9a157a7d45cbfb016d4427931e1d5345210f7a...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

jbachorik · 2021-11-19T00:01:36Z

src/hotspot/share/jfr/metadata/metadata.xml

@@ -1034,6 +1034,11 @@
    <Field type="string" name="name" label="Name" />
  </Event>

+  <Event name="ZThreadEvent" category="Java Virtual Machine, GC, Detailed" label="ZGC Thread Event" thread="true" experimental="true">


Can you add a description to the event?
For anyone coming from outside it would really help to understand what this event is supposed to represent.

Great idea.

jbachorik · 2021-11-19T00:01:36Z

src/jdk.jfr/share/conf/jfr/default.jfc

@@ -775,6 +775,11 @@
      <setting name="threshold">0 ms</setting>
    </event>

+    <event name="jdk.ZThreadEvent">


This is just a question - do we want/need to have this event enabled for the 'low overhead profiling' setup?

Yes. I always use default.jfc. The profile.jfc is creating too many allocation related events to make it usable when running with ZGC. I know that there has been some plans to fix that, but I don't know if that made it into JDK 17 or not.

stefank · 2021-11-19T08:46:27Z

I discussed the naming of this event with @pliden, and we decided to rename it to make it more clear that this was only intended for debugging/development of ZGC.

pliden

Looks good.

mgronlun · 2021-11-22T10:25:18Z

What's the overhead of this event being enabled in default.jfc with threshold=0? Do all users really need to have this experimental event enabled by default when running ZGC?

stefank · 2021-11-22T10:43:00Z

The overhead should be virtually zero, since no event is sent. Having this turned off by default makes this feature more annoying to use. Is this causing problems for the users?

mgronlun · 2021-11-22T10:45:59Z

Ah. So "debug" means only used in "development builds" of the VM? In that case, there is no problem.

stefank · 2021-11-22T10:49:07Z

No, this is more likely to be used in release builds to identify and measure performance issues in ZGC. It is intended for us during debugging and development of various features in ZGC.

stefank · 2021-11-22T10:49:40Z

Think of this similar to the UseNewCode flag.

stefank · 2021-11-24T08:23:27Z

Thanks for reviewing!
/integrate

openjdk · 2021-11-24T08:25:14Z

Going to push as commit 712b875.
Since your change was applied there have been 111 commits pushed to the master branch:

7b2d823: 8277503: compiler/onSpinWait/TestOnSpinWaitAArch64DefaultFlags.java failed with "OnSpinWaitInst with the expected value 'isb' not found."
7cb56a2: 8265796: vmTestbase/nsk/jdi/ObjectReference/referringObjects/referringObjects002/referringObjects002.java fails when running with JEP 416
24e586a: 8276764: Enable deterministic file content ordering for Jar and Jmod
ea85e01: 8271623: Omit enclosing instance fields from inner classes that don't use it
0320672: 8277451: java.lang.reflect.Field::set on static field with invalid argument type should throw IAE
e8acac2: 8277350: runtime/jni/checked/TestPrimitiveArrayCriticalWithBadParam.java times out
8a44e09: 8268725: jshell does not support the --enable-native-access option
7b67a49: 8261847: performance of java.lang.Record::toString should be improved
38802ad: 8254108: ciReplay: Support incremental inlining
64bdc84: 8277649: [BACKOUT] JDK-8277507 Add jlink.debug system property while launching jpackage tests to help diagonize recent intermittent failures
... and 101 more: https://git.openjdk.java.net/jdk/compare/9a9a157a7d45cbfb016d4427931e1d5345210f7a...master

Your commit was automatically rebased without conflicts.

openjdk · 2021-11-24T08:25:25Z

@stefank Pushed as commit 712b875.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

8277397: ZGC: Add JFR event for temporary latency measurements

85f9b14

openjdk bot added the rfr label Nov 18, 2021

openjdk bot added the hotspot label Nov 18, 2021

openjdk bot added hotspot-gc hotspot-jfr labels Nov 18, 2021

openjdk bot removed the hotspot label Nov 18, 2021

fisk approved these changes Nov 18, 2021

View changes

openjdk bot added the ready label Nov 18, 2021

jbachorik suggested changes Nov 19, 2021

View changes

stefank added 2 commits Nov 19, 2021

Review jbachorik

478c38a

Rename ZThreadEvent to ZThreadDebug

15f4d9a

pliden approved these changes Nov 19, 2021

View changes

fisk approved these changes Nov 19, 2021

View changes

jbachorik approved these changes Nov 20, 2021

View changes

mgronlun approved these changes Nov 22, 2021

View changes

openjdk bot closed this Nov 24, 2021

openjdk bot added integrated and removed ready rfr labels Nov 24, 2021

stefank deleted the 8277397_ZThreadEvent branch Jan 12, 2022

8277397: ZGC: Add JFR event for temporary latency measurements #6454

8277397: ZGC: Add JFR event for temporary latency measurements #6454

stefank commented Nov 18, 2021 •

edited by openjdk[bot] bot

stefank commented Nov 18, 2021

bridgekeeper bot commented Nov 18, 2021

openjdk bot commented Nov 18, 2021

openjdk bot commented Nov 18, 2021

mlbridge bot commented Nov 18, 2021 •

edited

stefank commented Nov 18, 2021

openjdk bot commented Nov 18, 2021

stefank commented Nov 18, 2021

openjdk bot commented Nov 18, 2021

stefank commented Nov 18, 2021

fisk left a comment

openjdk bot commented Nov 18, 2021 •

edited

jbachorik Nov 19, 2021

stefank Nov 19, 2021

jbachorik Nov 19, 2021

stefank Nov 19, 2021

stefank commented Nov 19, 2021

pliden left a comment

mgronlun commented Nov 22, 2021

stefank commented Nov 22, 2021

mgronlun commented Nov 22, 2021 •

edited

stefank commented Nov 22, 2021

stefank commented Nov 22, 2021

stefank commented Nov 24, 2021

openjdk bot commented Nov 24, 2021

openjdk bot commented Nov 24, 2021

8277397: ZGC: Add JFR event for temporary latency measurements #6454

8277397: ZGC: Add JFR event for temporary latency measurements #6454

Conversation

stefank commented Nov 18, 2021 • edited by openjdk[bot] bot

Progress

Issue

Reviewers

Reviewing

stefank commented Nov 18, 2021

bridgekeeper bot commented Nov 18, 2021

openjdk bot commented Nov 18, 2021

openjdk bot commented Nov 18, 2021

mlbridge bot commented Nov 18, 2021 • edited

Webrevs

stefank commented Nov 18, 2021

openjdk bot commented Nov 18, 2021

stefank commented Nov 18, 2021

openjdk bot commented Nov 18, 2021

stefank commented Nov 18, 2021

fisk left a comment

openjdk bot commented Nov 18, 2021 • edited

jbachorik Nov 19, 2021

Choose a reason for hiding this comment

stefank Nov 19, 2021

Choose a reason for hiding this comment

jbachorik Nov 19, 2021

Choose a reason for hiding this comment

stefank Nov 19, 2021

Choose a reason for hiding this comment

stefank commented Nov 19, 2021

pliden left a comment

mgronlun commented Nov 22, 2021

stefank commented Nov 22, 2021

mgronlun commented Nov 22, 2021 • edited

stefank commented Nov 22, 2021

stefank commented Nov 22, 2021

stefank commented Nov 24, 2021

openjdk bot commented Nov 24, 2021

openjdk bot commented Nov 24, 2021

stefank commented Nov 18, 2021 •

edited by openjdk[bot] bot

mlbridge bot commented Nov 18, 2021 •

edited

openjdk bot commented Nov 18, 2021 •

edited

mgronlun commented Nov 22, 2021 •

edited