RFR: 8203290: [PPC64, s390] Check functionality of JDK-8199712 (Flight Recorder) [v15]

[Tyler Steele]

On Tue, 25 Jan 2022 09:06:49 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Tyler Steele has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:
>> 
>>  - Merge branch 'master' into JDK-8203290
>>  - Implements JFR on AIX
>>    
>>    - Implements interfaces from os_perf.hpp in os_perf_aix.cpp
>>    - Updates libperfstat_aix to contain functionality needed by os_perf_aix
>>    - Implements missing functionality in loadlib_aix (Fixes failure noted
>>    by TestNativeLibraies.java)
>>    - Removes platform checks for --enable-feature-jfr (Now enable-able on
>>    all platforms)
>>    - Enables TestNetworkUtilizationEvent.java which now passes on AIX
>>    - Updates AIX JavaThread::pd_get_top_frame_for_profiling with changes from Linux
>
> src/hotspot/os/aix/os_perf_aix.cpp line 214:
> 
>> 212:   // populate cpu_stats && check that the expected number of records have been populated
>> 213:   if (ncpus != libperfstat::perfstat_cpu(&name_holder, all_lcpu_stats, sizeof(perfstat_cpu_t), ncpus)) {
>> 214:     FREE_RESOURCE_ARRAY(perfstat_cpu_t, all_lcpu_stats, ncpus);
> 
> ResourceArray are stack-based arenas. No need to free them manually (freeing is often a noop anyway unless the allocation is a the top of the arena). Very similar to those AutoReleasePools in Objective-C, if you know that.
> 
> The way to use them is don't release them. If those allocations don't escape the function (so, you don't return RA memory from the function), you can set a ResourceMark at the start of the function. That is an RAII object which will clear all RA objects allocated in and under this function upon return.
> 
> Arguably, you also could just use malloc and free here (NEW_C_HEAP_ARRAY and FREE_C_HEAP_ARRAY)

This is interesting, and definitely good to know. I have removed all FREE_RESOURCE_ARRAY calls and added a ResourceMark to the top of all procedures which use RESOURCE_ARRAYs.

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PR: https://git.openjdk.java.net/jdk/pull/6885