RFR: 8266217: ZGC: Improve the -Xlog:gc+init output for NUMA

[Thomas Schatzl]

On Thu, 29 Apr 2021 07:14:35 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>> This patch improves the -Xlog:gc+init output for NUMA, which is suggested by StefanK [1].
>> The implementation just follows how UseLargePages are setup and printed.
>> 
>> Before (in docker, not support get_mempolicy)
>> 
>> [0.007s][info][gc,init] Initializing The Z Garbage Collector
>> [0.007s][info][gc,init] Version: 17-internal+0-adhoc..jdk (fastdebug)
>> [0.007s][info][gc,init] NUMA Support: Disabled
>> ...
>> 
>> 
>> After (in docker, not support get_mempolicy)
>> 
>> [0.007s][info][gc,init] Initializing The Z Garbage Collector
>> [0.007s][info][gc,init] Version: 17-internal+0-adhoc..jdk (fastdebug)
>> [0.007s][info][gc,init] NUMA Support: Unsupported
>> ...
>> 
>> 
>> Testing:
>>   - tier1~3 on Linux/x64, no regression
>> 
>> Thanks.
>> Best regards,
>> Jie
>> 
>> 
>> [1] https://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2020-March/028927.html
>
> src/hotspot/share/gc/z/zNUMA.cpp line 41:
> 
>> 39: 
>> 40: const char* ZNUMA::to_string() {
>> 41:   switch (_state) {
> 
> Maybe consider to have a `static const char* strings[] = {"Enabled", "Unsupported", "Disabled" };` (in the correct order) constant here and index by the array (and maybe an assert to catch out of bounds access if/when adds an entry and forgets to update this list).
> This is typically more readable then a long switch case like this, but idk other people's opinions.

And of course it's not a particular important suggestion, feel free to ignore.

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PR: https://git.openjdk.java.net/jdk/pull/3778