RFR: 8231943: ZGC: Enable serviceability/dcmd/gc/RunGCTest

[Per Liden]

Hi Thomas,

On 10/16/19 10:07 AM, Thomas Schatzl wrote:
> Hi,
> 
> On 07.10.19 14:38, Per Liden wrote:
>> This test is currently disabled for ZGC, but it can easily be enabled 
>> by adjusting the expected log string. ZGC doesn't print "Pause Full", 
>> but it still prints the "(Diagnostic Command)" part.
>>
> Not sure if that checking only for that satisfies the requirements of 
> the test. I mean that this is a test to verify that jcmd executes (or 
> starts) a GC. I do not think checking for "(Diagnostic Command)" is 
> enough - it could be any diagnostic command that could be executed.

I don't think that's quite true, since the file we're greping in is the 
GC log (not stdout), which we know only contains stuff from gc=info. So, 
only if the GC itself is printing "(Diagnostic Command)" on gc=info 
level somewhere else is this a problem, which I would find somewhat 
surprising, no?

> 
> What does ZGC print here? Can the check be made more specific?

"Garbage Collection (Diagnostic Command)"

I opted to search for just "(Diagnostic Command)" mainly to keep the 
test GC agnostic. I don't have a strong opinion, but I don't believe 
making more specific greps will make the test more robust in practice, 
for the reason described above.

cheers,
Per

> 
>> Also, the test enables gc=debug logging, which is unnecessary since 
>> this is always printed on the gc=info level.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8231943
>> Webrev: http://cr.openjdk.java.net/~pliden/8231943/webrev.0
>>
> 
> Thanks,
>    Thomas