RFR: 8334492: DiagnosticCommands (jcmd) should accept %p in output filenames and substitute PID [v9]

[Kevin Walls]

On Tue, 23 Jul 2024 17:57:04 GMT, Sonia Zaldana Calles <szaldana at openjdk.org> wrote:

>> Hi all, 
>> 
>> This PR addresses [8334492](https://bugs.openjdk.org/browse/JDK-8334492) enabling jcmd diagnostic commands that issue an output file to accept the `%p` pattern in the file name and substitute it for the PID. 
>> 
>> This PR addresses the following diagnostic commands: 
>> - [x] Compiler.perfmap 
>> - [x] GC.heap_dump
>> - [x] System.dump_map
>> - [x] Thread.dump_to_file
>> - [x] VM.cds
>> 
>> Note that some jcmd diagnostic commands already enable this functionality (`JFR.configure, JFR.dump, JFR.start and JFR.stop`). 
>> 
>> I propose opening a separate issue to track updating the man page similarly to how it’s done for the JFR diagnostic commands. For example, 
>> 
>> 
>> filename         (Optional) Name of the file to which the flight recording data is
>>                    written when the recording is stopped. If no filename is given, a
>>                    filename is generated from the PID and the current date and is
>>                    placed in the directory where the process was started. The
>>                    filename may also be a directory in which case, the filename is
>>                    generated from the PID and the current date in the specified
>>                    directory. (STRING, no default value)
>> 
>>                    Note: If a filename is given, '%p' in the filename will be
>>                    replaced by the PID, and '%t' will be replaced by the time in
>>                    'yyyy_MM_dd_HH_mm_ss' format.
>> 
>> 
>> Unfortunately, per [8276265](https://bugs.openjdk.org/browse/JDK-8276265), sources for the jcmd manpage remain in Oracle internal repos so this PR can’t address that. 
>> 
>> Testing: 
>> 
>> - [x] Added test case passes. 
>> - [x] Modified existing VM.cds tests to also check for `%p` filenames. 
>> 
>> Looking forward to your comments and addressing any diagnostic commands I might have missed (if any). 
>> 
>> Cheers, 
>> Sonia
>
> Sonia Zaldana Calles has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 15 commits:
> 
>  - Merge master
>  - Fixing formatting
>  - Inlining buffer and making field private
>  - Reverting to functional changes in parserTests.cpp
>  - Error messaging format
>  - Fixing memory leak
>  - Fixing pointer style, s/NULL/nullptr, and exception
>  - Cleaning up parserTests.cpp
>  - Missing copyright header update
>  - Adding tests for file dcmd argument
>  - ... and 5 more: https://git.openjdk.org/jdk/compare/2f2223d7...52ca557d

Is the help output working OK?
Do these commands' help outputs show the new %p filename?
I think it's good that they would.  We should expect users of these commands to implicity understand a %p although we can still explain it, e.g. in a separate update in the man page.

I just think we should be explicit that the help output is changing.

In src/hotspot/share/runtime/java.cpp:    if (DumpPerfMapAtExit) { CodeCache::write_perf_map(....

It may need to pass DEFAULT_PERFMAP_FILENAME (and tty).

Do you have the change from JDK-8327054 merged into this branch?

src/hotspot/share/services/diagnosticArgument.hpp line 65:

> 63: class FileArgument {
> 64:   private:
> 65:     char _name[1024];

Probably JVM_MAXPATHLEN (which might also be 1024).

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PR Comment: https://git.openjdk.org/jdk/pull/20198#issuecomment-2247558224
PR Comment: https://git.openjdk.org/jdk/pull/20198#issuecomment-2247560119
PR Review Comment: https://git.openjdk.org/jdk/pull/20198#discussion_r1689545224