JFR chunks 2.0/2.1 specs?

[Erik Gahlin]

Hi,

There is no spec. for the JFR file format. The change between 2.0 and 2.1 only applies to streaming. Once a recording is complete the format is exactly the same. What was added was the use of a few bits extension bits in the chunk header. You can do a diff of ChunkHeader to see the difference.

The flush marker in the check point event, not used prior to JDK 14, but added in JDK 11 to future proof the format, now contains type information about a check point. This can be used to optimize parsing when streaming. You can see the CheckpointType class.

Erik
________________________________
From: hotspot-jfr-dev <hotspot-jfr-dev-retn at openjdk.java.net> on behalf of Jie Kang <jkang at redhat.com>
Sent: Monday, August 30, 2021 9:20 PM
To: hotspot-jfr-dev at openjdk.java.net <hotspot-jfr-dev at openjdk.java.net>
Subject: JFR chunks 2.0/2.1 specs?

Hi all,

Does the jfr chunk have a spec (especially to compare 2.0 vs 2.1) that
can be shared?  It would make things a little quicker for me over
examining the chunk writing implementations in 11 and 17.


Thanks,
--
Jie Kang
Red Hat Canada
https://keybase.io/jkang
1F5B34F61EF92DB4DCDDF195F034C81F60D402AA