RFR: JDK-8068589: GCCause should distinguish jcmd GC.run from System.gc()

Yasumasa Suenaga yasuenag at gmail.com
Sun Jan 25 15:11:31 UTC 2015


Hi Kirk,

I think the System.gc() call which is invoked by jcmd is special case and I want to
distinguish it.
Programmer can call System.gc() from their code. But GC which is invoked by jcmd is NOT explicitly call by programmer.

Indeed, SystemGCDCmd will call System.gc() (same meaning).
However, I think it has different meaning from System.gc() call from source code.


Thanks,

Yasumasa


On 2015/01/25 22:56, Kirk Pepperdine wrote:
> Hi,
> 
> IMHO, if a System.gc() is being called then the cause should be System.gc(). If we start down the road of differentiating between the various causes of calls to System.gc() this will turn in a nightmare!
> 
> Indeed as I look at the patch it’s curious that it’s up to the caller to determine is calls to System.gc() have been suppressed. I would have expected the collect() call to make the decision as to should the call be honored or not.
> 
>   void SystemGCDCmd::execute(DCmdSource source, TRAPS) {
>     if (!DisableExplicitGC) {
>      Universe::heap()->collect(GCCause::_jcmd_gc_run);
>     } else {
>       output()->print_cr("Explicit GC is disabled, no GC has been performed.");
>     }
> 
> 
> 
> Kind regards,
> Kirk Pepperdine
> 
> On Jan 25, 2015, at 2:15 PM, Yasumasa Suenaga <yasuenag at gmail.com <mailto:yasuenag at gmail.com>> wrote:
> 
>> Hi all,
>>
>> GCCause which is printed in gc log is "System.gc()" when jcmd GC.run is invoked.
>> I think that GCCause which is caused by jcmd GC.run should be different from System.gc() .
>>
>> I uploaded webrev for this enhancement:
>> http://cr.openjdk.java.net/~ysuenaga/JDK-8068589/webrev.00/
>>
>> This patch prints "jcmd GC.run" to gc log when jcmd GC.run is invoked.
>>
>>
>> Could you review it?
>>
>>
>> Thanks,
>>
>> Yasumasa
> 


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