RFR (XS) 8222818: NMT summary could show the GC in use

[Kodewerk]

Hi Eric,

G1GC is obviously GC so why not reduce to...

-                G1GC -  (reserved=379090KB, committed=93254KB)
                               (malloc=39218KB #2194)
                               (mmap: reserved=339872KB, committed=54036KB)

Kind regards,
Kirk




> On Apr 23, 2019, at 11:53 AM, Eric Caspole <eric.caspole at oracle.com> wrote:
> 
> Hi Zhengyu,
> Hopefully this email comes through in monospace, the alignment is OK for me:
> 
> 
> currently:
> 
> -                        GC (reserved=379056KB, committed=93220KB)
>                            (malloc=39184KB #2159)
>                            (mmap: reserved=339872KB, committed=54036KB)
> 
> 
> My version:
> 
> 
> -                GC - g1 gc (reserved=379090KB, committed=93254KB)
>                            (malloc=39218KB #2194)
>                            (mmap: reserved=339872KB, committed=54036KB)
> 
> 
> so it is aligned going to the left off the parenthesis like the current version. Is that what you mean? I like the way the GC stands out like this but it is OK to put it in the parentheses on the right.
> 
> Thanks,
> Eric
> 
> 
> 
> On 4/22/19 21:57, Zhengyu Gu wrote:
>> On 4/22/19 8:19 PM, David Holmes wrote:
>>> Hi Eric,
>>> 
>>> On 23/04/2019 8:13 am, Eric Caspole wrote:
>>>> Hi, could I have reviews and any opinions on this little change to show the GC name in the NMT output, as this helps us to more easily triage performance data.
>>> 
>>> The idea seems fine.
>>> 
>>> For the implementation wouldn't it be simpler to do something like:
>>> 
>>> if (flag == mtGC) {
>>>    out->print("%s - %s (", NMTUtil::flag_to_name(flag),
>>>                            GCConfig::hs_err_name());
>>> } else {
>>>    out->print("-%26s (", NMTUtil::flag_to_name(flag));
>>> }
>>> 
>> Yes, this is simpler.
>> I don't like where the name is placed, it screws up section alignments. I would prefer to place name inside parenthesis. e.g.
>> - GC (g1 gc reserved=379056KB, committed=93220KB)
>> Thanks,
>> -Zhengyu
>>> and skip the need for a local buffer and snprintf?
>>> 
>>> Aside: it's probably used in enough different contexts that GCConfig::hs_err_name should be renamed.
>>> 
>>> Also if the VM terminates during initialization is it possible for this code to be executed before the GCConfig has been setup? And if so how will it behave?
>>> 
>>> Thanks,
>>> David
>>> 
>>>> This passed tier 1 and 2.
>>>> Thanks,
>>>> Eric
>>>> 
>>>> 
>>>> JBS:
>>>> https://bugs.openjdk.java.net/browse/JDK-8222818
>>>> 
>>>> webrev:
>>>> http://cr.openjdk.java.net/~ecaspole/JDK-8222818/02/webrev/