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

Mon Dec 9 09:05:32 UTC 2019

Hi Christoph,
  I was on vacation last week, sorry for the late reply.
  In fact, the backport of 8185525 for 8u was requested by @Andrey at first (https://mail.openjdk.java.net/pipermail/jdk8u-dev/2019-September/010204.html)
  For the sake of consistency, I made this backport for 11u.
  And in my opinion, these events are not very useful for users indeed.

Thanks,
Denghui Dong
------------------------------------------------------------------
From:Langer, Christoph <christoph.langer at sap.com>
Send Time:2019年12月6日(星期五) 16:32
To:Erik Gahlin <erik.gahlin at oracle.com>; jdk-updates-dev <jdk-updates-dev at openjdk.java.net>
Cc:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>
Subject:RE: [11u] RFR 8185525: Add JFR event for DictionarySizes

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> 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>; jdk-updates-dev <jdk-updates-dev at openjdk.java.net>
 Cc: Andrew Haley <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>>; jdk-updates-dev <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>>
 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>>; Langer, Christoph <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>>
 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>>; jdk-updates-dev <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>> 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>>
 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