Need comments on JEP-158: Unified JVM Logging

[Chris Newland]

Hi Fredrik,

The discussion I had with David Holmes and John Rose on hotspot-dev back
in February might be relevant to this JEP:
http://mail.openjdk.java.net/pipermail/hotspot-dev/2014-February/012718.html

I'm the author of a JITWatch[1], a JIT compiler log analysis tool which
relies on -XX:+TraceClassLoading -XX:+LogCompilation -XX:+PrintAssembly
all being present in hotspot.log

Occasionally the lack of thread safety in the VM logging presents me with
jumbled output:

[Entry Point]
[Constants]
   # {method} 'ind
<writer thread='3340'/>
[Loaded sun.nio.cs.ThreadLocalCoders from C:\Program
Files\Java\jre7\lib\rt.jar]
<writer thread='2660'/>
exOf' '(II)I' in 'java/lang/String'
   # this:     ecx       = 'java/lang/String'
   # parm0:    edx       = int
   # parm1:    [sp+0x20]   = int  (sp of caller)
   0x009e07e0: nop

The JEP goal of no interleaving would fix this problem but if the locking
adds too much cost/complexity then John's suggestion of tagging partial
lines would be a great help to log tool writers.

Otherwise my only comment is that the goals look like a massive
improvement to current VM logging but for post-execution log tool writers
it is also useful for end users to be able to easily locate and load a
single log file.

Kind regards,

Chris

[1] https://github.com/AdoptOpenJDK/jitwatch

>>> ---------- Forwarded message ----------
>>> From: Fredrik Arvidsson <fredrik.arvidsson at oracle.com>
>>> Date: 16 May 2014 09:47
>>> Subject: Need comments on JEP-158: Unified JVM Logging
>>> To: "serviceability-dev at openjdk.java.net
>>> serviceability-dev at openjdk.java.net"
>>> <serviceability-dev at openjdk.java.net>,
>>> hotspot-dev at openjdk.java.net
>>>
>>>
>>> Hi all
>>> Please help me review this updated version of the JEP-158 Unified JVM
>>> Logging that was pushed today to the JEP repository.
>>>
>>> Since the service posting the JEPs to http://openjdk.java.net/jeps/
>>> site
>>> seems to be non working at the moment I am linking directly to the HG
>>> repository instead.
>>>
>>> The updated JEP can be found here in raw markdown format:
>>> http://hg.openjdk.java.net/jep/jeps/file/b04a394c4df4/jep-158.md
>>>
>>> Primarily I would like to have feedback on the overall functionality
>>> scope, the logging API and the command line argument format. All type
>>> of
>>> comments are of course welcome, but I would like to stay away from any
>>> implementation specifics at this point.
>>>
>>> I have a POC implementation which is nearly feature complete up and
>>> running and it looks good so far.
>>>
>>> /Fredrik
>>>
>>>