RFR: 8314029: Add file name parameter to Compiler.perfmap [v8]

[Dean Long]

On Mon, 11 Dec 2023 22:41:56 GMT, Yi-Fan Tsai <duke at openjdk.org> wrote:

>> `jcmd Compiler.perfmap` uses the hard-coded file name for a perf map: `/tmp/perf-%d.map`. This change adds an optional argument for specifying a file name.
>> 
>> `jcmd PID help Compiler.perfmap` shows the following usage.
>> 
>> 
>> Compiler.perfmap
>> Write map file for Linux perf tool.
>> 
>> Impact: Low
>> 
>> Syntax : Compiler.perfmap  [<filename>]
>> 
>> Arguments:
>>         filename : [optional] Name of the map file (STRING, no default value)
>> 
>> 
>> The following section of man page is also updated. (`man -l src/jdk.jcmd/share/man/jcmd.1`)
>> 
>> 
>>        Compiler.perfmap [arguments] (Linux only)
>>               Write map file for Linux perf tool.
>> 
>>               Impact: Low
>> 
>>               arguments:
>> 
>>               · filename: (Optional) Name of the map file (STRING, no default value)
>> 
>>               If filename is not specified, a default file name is chosen using the pid of the target JVM process.  For example, if the pid is 12345,  then
>>               the default filename will be /tmp/perf-12345.map.
>
> Yi-Fan Tsai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update copyright of PerfMapTest

The man page says "no default value" but then right below describes the default value, which is confusing.  I would remove "no default value".
The code already deals with patterns, so why not allow a pattern like /dir/perf-%x.map and document that the platform-specific process id will be passed to String.format() to expand any formatting tokens in the string?

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PR Comment: https://git.openjdk.org/jdk/pull/15871#issuecomment-1854683037