RFR: 8314029: Add file name parameter to Compiler.perfmap [v5]

[Chris Plummer]

On Tue, 28 Nov 2023 23:25:27 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 man page of jcmd will be updated in a separate PR.
>
> Yi-Fan Tsai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Apply man changes

src/hotspot/share/code/codeCache.cpp line 1809:

> 1807: }
> 1808: 
> 1809: void CodeCache::write_perf_map(const char* filename) {

Why not have a `filename == nullptr` indicate that the default should be used. Then you don't need CodeCache::DefaultPerfMapFile. You can just have a private `CodeCache::defaultPerfmapFileName()` method.

src/hotspot/share/code/codeCache.hpp line 232:

> 230:     const char* name() const  { return _name; }
> 231:   };)
> 232: 

Multi-line sections like this should really use `#ifdef LINUX`.

src/hotspot/share/runtime/java.cpp line 507:

> 505:   if (DumpPerfMapAtExit) {
> 506:     CodeCache::DefaultPerfMapFile file;
> 507:     CodeCache::write_perf_map(file.name());

It's a bit inconsistent to support a user provided filename for the dcmd but not when using `DumpPerfMapAtExit`. Perhaps add `PerfMapFilename`. I'm not insisting, but something to consider. Would be good for the compiler team to comment on this.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15871#discussion_r1412585004
PR Review Comment: https://git.openjdk.org/jdk/pull/15871#discussion_r1412579044
PR Review Comment: https://git.openjdk.org/jdk/pull/15871#discussion_r1412582441