[11u] RFR 8185525: Add JFR event for DictionarySizes

Fri Dec 6 08:32:03 UTC 2019

Hi Erik,

thanks for you input on this. I guess you have a very good point here – the bar for backporting new events should be quite high.

@Denghui: Is there any motivation for this backport from your end that comes from support requirements/customer incidents?

Thanks
Christoph

From: Erik Gahlin <erik.gahlin at oracle.com>
Sent: Freitag, 6. Dezember 2019 05:14
To: jdk-updates-dev <jdk-updates-dev at openjdk.java.net>
Cc: Denghui Dong <denghui.ddh at alibaba-inc.com>; Langer, Christoph <christoph.langer at sap.com>
Subject: Re: [11u] RFR 8185525: Add JFR event for DictionarySizes

Hi,

What’s nice about jFR is that the file format is self-describing, so a program like JMC can see what events exist or does not exist in a recording.

Still, I think the bar should be high when backporting events. Not just for stability reasons, but If different JDK distributions or update releases have different events, it will confuse users, or lead to bugs, when users switch from one JDK to another.

In my opinion, events should only be backported if support engineers truly need them to diagnose a certain type of bugs in the JVM/JDK. For this happen, there should be at least a few incidents where they have come to the conclusion that the events are needed. If there are no such real cases, the events should not be backported.

My $.02

Erik

On 5 Dec 2019, at 23:28, Langer, Christoph <christoph.langer at sap.com<mailto:christoph.langer at sap.com>> wrote:

Hi Denghui,

since no objections were raised, I’m approving JDK-8185525. I’ll push it, once I get approval for JDK-8223599 as well. Testing in our system doesn’t show regressions.

Cheers
Christoph

From: Langer, Christoph
Sent: Freitag, 22. November 2019 00:30
To: Denghui Dong <denghui.ddh at alibaba-inc.com<mailto:denghui.ddh at alibaba-inc.com>>; jdk-updates-dev <jdk-updates-dev at openjdk.java.net<mailto:jdk-updates-dev at openjdk.java.net>>
Cc: Andrew Haley <aph at redhat.com<mailto:aph at redhat.com>>
Subject: RE: [11u] RFR 8185525: Add JFR event for DictionarySizes

Hi,

we had a discussion on this list regarding JFR feature requests. As a summary, I take we should

 1.  Generally reject backports of new features from higher releases if these are too extensive or require lots of prerequisites. Exceptions might be made if the feature to be backported exists in lower releases (e.g. OpenJDK8u after the JFR backport has been integrated)
 2.  Be very careful when it comes to extensive bugfixes for existing features

This fix is actually on the edge of category a), since it is a new feature and it is not trivial in its nature. It needs some manual adaption but fortunately no other prerequisites.

Given that Denghui has done the effort of backporting it already and the patch together with another small follow up fix runs through our regression testing at SAP successfully, I could imagine to allow it going in to 11u. I would then like to see it submitted at the early stage of the 11.0.7 cycle.

So, @all, please raise objections to this decision until next Friday, 29th of November. If I don’t hear any, I’ll approve it after that date.

Thanks
Christoph

From: Langer, Christoph
Sent: Mittwoch, 30. Oktober 2019 15:41
To: Denghui Dong <denghui.ddh at alibaba-inc.com<mailto:denghui.ddh at alibaba-inc.com><mailto:denghui.ddh at alibaba-inc.com>>; jdk-updates-dev <jdk-updates-dev at openjdk.java.net<mailto:jdk-updates-dev at openjdk.java.net><mailto:jdk-updates-dev at openjdk.java.net>>
Subject: RE: [11u] RFR 8185525: Add JFR event for DictionarySizes

Hi Denghui,

sorry for the late reply.

I was discussing with Andrew Haley about JFR backports. He encouraged to do a general discussion on the mailing list about the policy regarding non-trivial JFR related backports, which I started just today:
https://mail.openjdk.java.net/pipermail/jdk-updates-dev/2019-October/002053.html
Let’s see if there’s any feedback…

Best regards
Christoph

From: Denghui Dong <denghui.ddh at alibaba-inc.com<mailto:denghui.ddh at alibaba-inc.com><mailto:denghui.ddh at alibaba-inc.com>>
Sent: Dienstag, 22. Oktober 2019 04:09
To: jdk-updates-dev <jdk-updates-dev at openjdk.java.net<mailto:jdk-updates-dev at openjdk.java.net><mailto:jdk-updates-dev at openjdk.java.net>>; Langer, Christoph <christoph.langer at sap.com<mailto:christoph.langer at sap.com><mailto:christoph.langer at sap.com>>
Subject: Re: [11u] RFR 8185525: Add JFR event for DictionarySizes

Hi Christoph,
 What's the status of this backport ?
 By the way, the previous webrev didn't contain the original commit, so I uploaded a new one in http://cr.openjdk.java.net/~ddong/8185525/webrev/

Thanks,
Denghui Dong
------------------------------------------------------------------
From:Langer, Christoph <christoph.langer at sap.com<mailto:christoph.langer at sap.com><mailto:christoph.langer at sap.com>>
Send Time:2019年10月8日(星期二) 22:34
To:董登辉(卓昂) <denghui.ddh at alibaba-inc.com<mailto:denghui.ddh at alibaba-inc.com><mailto:denghui.ddh at alibaba-inc.com>>; jdk-updates-dev <jdk-updates-dev at openjdk.java.net<mailto:jdk-updates-dev at openjdk.java.net><mailto:jdk-updates-dev at openjdk.java.net>>
Subject:RE: [11u] RFR 8185525: Add JFR event for DictionarySizes

Hi Denghui,

this is quite a large JFR enhancement.

Looking at the 11u webrev, I didn't see any obvious issues although there are obviously quite some alterations from the original patch. I'll run it through our regression testing.

However, in any case, we need to carefully decide if and when we allow this patch to jdk11u-dev. I'll get back to you soon.

Best regards
Christoph

-----Original Message-----
From: jdk-updates-dev <jdk-updates-dev-bounces at openjdk.java.net<mailto:jdk-updates-dev-bounces at openjdk.java.net><mailto:jdk-updates-dev-bounces at openjdk.java.net>> On
Behalf Of Denghui Dong
Sent: Donnerstag, 26. September 2019 17:03
To: jdk-updates-dev <jdk-updates-dev at openjdk.java.net<mailto:jdk-updates-dev at openjdk.java.net><mailto:jdk-updates-dev at openjdk.java.net>>
Subject: [11u] RFR 8185525: Add JFR event for DictionarySizes

Hi all,
 Please review this backport, original patch doesn't apply cleanly, because
SymbolTable has made some changes in upstream (I think it's not necessary
to backport those changes)
and class ClassLoaderDataGraph is located in different files.
11u-webrev:
http://cr.openjdk.java.net/~wzhuo/8185525/webrev.00/
Original bug:
https://bugs.openjdk.java.net/browse/JDK-8185525
http://hg.openjdk.java.net/jdk/jdk/rev/865ec913f916
Testing: test/jdk/jdk/jfr/event/runtime/TestTableStatisticsEvent.java

Thanks,
Denghui Dong