Re: RFR: 8237499: JFR event for the location where a new thread starts

[Denghui Dong]

Hi Erik,
 > set stackTrace="true" in metadata.xml 
 Actually, I thought about it before. But two thing let me add a new field explicitly finally: 
1. EventThreadStart was also posted in jni.cpp, and there is no need to record the stack trace, we cannot control it if setting stackTrace="true".
2.  I think adding an explicit filed can make us and users clear that the stack trace isn't recorded from the new thread but the parent thread. And
there are also other events that have an explicit stack trace field(e.g. ExecutionSample).

 > change the label of the thread field from "Java Thread" to "New Thread"
 It makes sense, I will update it.

Thanks
Denghui Dong
------------------------------------------------------------------
From:Erik Gahlin <erik.gahlin at oracle.com>
Send Time:2020年1月23日(星期四) 21:44
To:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>; hotspot-jfr-dev <hotspot-jfr-dev at openjdk.java.net>
Subject:Re: RFR: 8237499: JFR event for the location where a new thread starts

Hi Denghui, 

 Would it be possible to set stackTrace="true" in metadata.xml instead of adding a new field explicitly? 
This allows users to turn on and off stack traces. You could check if stack trace is enabled and only record if needed.

 I think it would be good to change the label of the thread field from "Java Thread" to "New Thread".

 Thanks
 Erik

 On 2020-01-19 09:13, Denghui Dong wrote:
Hi Erik
  The webrev has been updated.
  I reuse the event type "EventThreadStart" to report the location where a new thread starts.
  Add two fields "stackTrace" and "parentThread" to EventThreadStart.
  Please help review it, thanks.

Best Regards
Denghui Dong
------------------------------------------------------------------
From:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>
Send Time:2020年1月18日(星期六) 21:25
To:Erik Gahlin <erik.gahlin at oracle.com>; hotspot-jfr-dev <hotspot-jfr-dev at openjdk.java.net>
Subject:Re: RFR: 8237499: JFR event for the location where a new thread starts

Hi Erik,
  Do you mean that we should reuse EventThreadStart rather than a new event? It's a good idea, I will try it.

Thanks
Denghui Dong
------------------------------------------------------------------
From:Erik Gahlin <erik.gahlin at oracle.com>
Send Time:2020年1月18日(星期六) 21:12
To:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>
Cc:hotspot-jfr-dev <hotspot-jfr-dev at openjdk.java.net>
Subject:Re: RFR: 8237499: JFR event for the location where a new thread starts

 Hi Denghui, 

 This will be useful, but I wonder if we shouldn’t extend the Thread Start event with stack trace and the parent thread? It will require some additional logic, but it would be a cleaner solution.

 Thanks
 Erik

 > On 18 Jan 2020, at 12:19, Denghui Dong <denghui.ddh at alibaba-inc.com> wrote:
 > 
 > Hi,
 > 
 > Could I have a review of a change that introduces an event for the location where a new thread starts.
 > 
 > Summary:
 > There is already an event for thread start(EventThreadStart), but this event is committed in the new thread,
 > so users can't know the location where the thread starts, hence, it's necessary to introduce another event, 
 > it would be useful if the application exists thread leak problem.
 > 
 > Bug: https://bugs.openjdk.java.net/browse/JDK-8237499
 > Webrev: http://cr.openjdk.java.net/~ddong/8237499/
 > 
 > Thanks
 > Denghui Dong
 >