On Mon, 15 Jan 2024 04:28:15 GMT, Ioi Lam <ik...@openjdk.org> wrote:
>> Ugghh! So the help text is an actual stringification of the actual default
>> value of the "field", whereas in this case the real default value comes from
>> passing null to `CodeCache::write_perf_map`. So we need this hack to deal
>> with that. That is truly awful IMO. The only way to cleanly address that is
>> to expand things so that you can set an actual help string to be used.
>
> This check is problematic:
>
>
> if (strncmp(filename, DEFAULT_PERFMAP_FILENAME,
> strlen(DEFAULT_PERFMAP_FILENAME)) == 0)
>
>
> Because it cannot tell whether `filename` was explicitly given by the user.
> As a result, if the user specifies:
>
>
> jcmd 1234 perfmap '/tmp/perf-<pid>.map'
>
>
> the file will be written as `/tmp/perf-1234.map`, but if the user specifies
>
>
> jcmd 1234 perfmap '/tmp/<pid>-perf.map'
>
>
> then the file will be written as `/tmp/<pid>-perf.map`.
>
> This gives the confusing impression that the string `<pid>` is sometimes
> substituted and sometimes not.
>
> I think it's better to do this (similarly for the `VM.cds` case):
>
>
> void PerfMapDCmd::execute(DCmdSource source, TRAPS) {
> CodeCache::write_perf_map(_filename.is_set() ? _filename.value() : nullptr);
> }
>
>
> This essentially makes the JVM behavior exactly the same as before, so I
> think we can change the JBS issue title to something like "Clarify docs for
> filename parameter to Compiler.perfmap and VM.cds".
@iklam but IIUC that does not address the issue of updationg the help output.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/17359#discussion_r1452007868
