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

[Zhengyu Gu]

On 4/23/19 2:53 PM, Eric Caspole 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.

Different GC has different name, it is hard to get them all aligned 
right, and it does not worth the effort.

So, my suggestion is to place GC name inside parentheses, and you don't 
have to deal with indents to the left.

e.g.


-                     GC (reserved=379056KB, committed=93220KB by g1 gc)
                           (malloc=39184KB #2159)
                           (mmap: reserved=339872KB, committed=54036KB)


Thanks,

-Zhengyu

> 
> 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/