RFR: 8254723: add diagnostic command to write Linux perf map file [v2]

[Nick Gasson]

On Wed, 21 Oct 2020 04:34:44 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>> Nick Gasson has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update for review comments
>
> src/hotspot/share/code/codeCache.cpp line 1562:
> 
>> 1560: }
>> 1561: 
>> 1562: void CodeCache::write_perf_map(outputStream* st) {
> 
> Should this code (and changes in header files) be included for Linux only? (`#ifdef LINUX` like the change in diagnosticCommand.cpp)

I'm not sure, I didn't want to add too much `#ifdef` mess. The code will compile on other platforms, it just won't be called. Better to add `#ifdef`s around all of it?

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PR: https://git.openjdk.java.net/jdk/pull/760