RFR(XXXS): 7168294: G1: Some Full GCs incorrectly report GC cause as "No GC"

[Bengt Rutisson]

Hi John,

Looks good!

Thanks for finding out where the No GC came from! I know I had seen it 
in some log output.

Bengt

On 2012-05-12 00:37, John Cuthbertson wrote:
> Hi Everyone,
>
> Can I have a couple of volunteers review this code change? The webrev 
> can be found at: http://cr.openjdk.java.net/~johnc/7168294/webrev.0/
>
> Summary:
> Basically the VM_G1CollectForAllocation VM operation was not setting 
> the GC cause in the heap structure and so the cause would come out as 
> "No GC". This one line change makes VM_G1CollectForAllocation match 
> the other 'leaf' G1 VM operations.
>
> Testing: GCOld
>
> Before:
>
> 9.239: [Full GC (No GC) 128M->125M(128M), 9.0804393 secs]
> 18.837: [Full GC (No GC) 127M->127M(128M), 7.9413652 secs]
> 26.778: [Full GC (No GC) 127M->127M(128M), 7.9419157 secs]
> 34.731: [Full GC (No GC) 127M->127M(128M), 8.0385112 secs]
> 42.770: [Full GC (No GC) 127M->127M(128M), 7.9215393 secs]
> 50.702: [Full GC (No GC) 127M->127M(128M), 9.0424004 secs]
> 59.744: [Full GC (No GC) 127M->127M(128M), 7.9409172 secs]
>
> After:
>
> 9.357: [Full GC (Allocation Failure) 128M->125M(128M), 9.1094425 secs]
> 18.976: [Full GC (Allocation Failure) 127M->127M(128M), 7.9846687 secs]
> 26.961: [Full GC (Allocation Failure) 127M->127M(128M), 7.9409885 secs]
> 34.913: [Full GC (Allocation Failure) 127M->127M(128M), 8.0551207 secs]
> 42.968: [Full GC (Allocation Failure) 127M->127M(128M), 7.9402328 secs]
> 50.919: [Full GC (Allocation Failure) 127M->127M(128M), 9.0121452 secs]
> 59.932: [Full GC (Allocation Failure) 127M->127M(128M), 7.9184263 secs]
>
> Thanks,
>
> JohnC