RFR: JDK-8148736: Let the G1 heap transition log regions instead of bytes

[Bengt Rutisson]

Another update to the webrev:
http://cr.openjdk.java.net/~brutisso/8148736/webrev.02/

As discussed in the email thread for "RFR: JDK-8148735: Simplify 
G1CollectorPolicy::max_region()​" I will add the 
G1CollectorPolicy::max_survivor_regions() method in this change instead.

Thanks,
Bengt

On 2016-02-01 13:48, Bengt Rutisson wrote:
>
> Hi again,
>
> I realized that the two macros EXT_SIZE_FORMAT and EXT_SIZE_PARAMS are 
> unused. Their usage was removed earlier, but since I am changing the 
> code very close by, I thought I can remove them in this change as well.
>
> Here's an updated webrev where these macros are removed as well:
> http://cr.openjdk.java.net/~brutisso/8148736/webrev.01/
>
> Thanks,
> Bengt
>
> On 2016-02-01 11:18, Bengt Rutisson wrote:
>>
>> Hi everyone,
>>
>> Could I have a couple of reviews for this change?
>>
>> http://cr.openjdk.java.net/~brutisso/8148736/webrev.00/
>> https://bugs.openjdk.java.net/browse/JDK-8148736
>>
>> (Note: the webrev is based on top of the change for JDK-8148733, 
>> JDK-8148734 and JDK-8148735 that are also currently out for review.)
>>
>> As described in JDK-8147976 the way G1 now logs the used memory for 
>> eden, survivor, old and humongous can be confusing. It does not 
>> necessarily add up to the same value as the overall heap usage.
>>
>> Instead log the number of regions each space is using. This should 
>> reduce the confusion. At trace level the exact usage can be logged.
>>
>> The current logging (running with -Xlog:gc*) looks like this:
>>
>> [1,395s][info   ][gc,start    ] GC(17) Pause Initial Mark (G1 
>> Evacuation Pause) (1,395s)
>> [1,417s][info   ][gc,heap     ] GC(17) Eden: 61440K->0K(61440K)
>> [1,417s][info   ][gc,heap     ] GC(17) Survivor: 4096K->4096K(8192K)
>> [1,417s][info   ][gc,heap     ] GC(17) Old: 61440K->61440K
>> [1,417s][info   ][gc,heap     ] GC(17) Humongous: 0K->0K
>> [1,417s][info   ][gc,metaspace] GC(17) Metaspace: 2967K->2967K(1056768K)
>> [1,417s][info   ][gc          ] GC(17) Pause Initial Mark (G1 
>> Evacuation Pause) 123M->63M(128M) (1,395s, 1,417s) 22,030ms
>> [1,417s][info   ][gc,cpu      ] GC(17) User=0,15s Sys=0,00s Real=0,02s
>>
>>
>> With the proposed change it will look like this:
>>
>> [1,391s][info   ][gc,start    ] GC(17) Pause Initial Mark (G1 
>> Evacuation Pause) (1,391s)
>> [1,407s][info   ][gc,heap     ] GC(17) Eden regions: 59->0(59)
>> [1,407s][info   ][gc,heap     ] GC(17) Survivor regions: 5->5(8)
>> [1,407s][info   ][gc,heap     ] GC(17) Old regions: 59->59
>> [1,407s][info   ][gc,heap     ] GC(17) Humongous regions: 0->0
>> [1,407s][info   ][gc,metaspace] GC(17) Metaspace: 2967K->2967K(1056768K)
>> [1,408s][info   ][gc          ] GC(17) Pause Initial Mark (G1 
>> Evacuation Pause) 121M->63M(128M) (1,391s, 1,408s) 16,632ms
>> [1,408s][info   ][gc,cpu      ] GC(17) User=0,15s Sys=0,01s Real=0,02s
>>
>>
>> and if you run with -Xlog:gc*,gc+heap=trace you will get this:
>>
>> [1,391s][trace  ][gc,heap     ] GC(17) Heap before GC invocations=17 
>> (full 0):
>> [1,391s][trace  ][gc,heap     ] GC(17)  garbage-first heap total 
>> 131072K, used 124885K [0x00000000f8000000, 0x00000000f8100400, 
>> 0x0000000100000000)
>> [1,391s][trace  ][gc,heap     ] GC(17)   region size 1024K, 64 young 
>> (65536K), 5 survivors (5120K)
>> [1,391s][trace  ][gc,heap     ] GC(17)  Metaspace used 2967K, 
>> capacity 4562K, committed 4864K, reserved 1056768K
>> [1,391s][trace  ][gc,heap     ] GC(17)   class space used 277K, 
>> capacity 386K, committed 512K, reserved 1048576K
>> [1,391s][info   ][gc,start    ] GC(17) Pause Initial Mark (G1 
>> Evacuation Pause) (1,391s)
>> [1,407s][info   ][gc,heap     ] GC(17) Eden regions: 59->0(59)
>> [1,407s][trace  ][gc,heap     ] GC(17)  Used: 0K, Waste: 0K
>> [1,407s][info   ][gc,heap     ] GC(17) Survivor regions: 5->5(8)
>> [1,407s][trace  ][gc,heap     ] GC(17)  Used: 4385K, Waste: 734K
>> [1,407s][info   ][gc,heap     ] GC(17) Old regions: 59->59
>> [1,407s][trace  ][gc,heap     ] GC(17)  Used: 60331K, Waste: 85K
>> [1,407s][info   ][gc,heap     ] GC(17) Humongous regions: 0->0
>> [1,407s][trace  ][gc,heap     ] GC(17)  Used: 0K, Waste: 0K
>> [1,407s][info   ][gc,metaspace] GC(17) Metaspace: 2967K->2967K(1056768K)
>> [1,407s][trace  ][gc,heap     ] GC(17) Heap after GC invocations=18 
>> (full 0):
>> [1,408s][trace  ][gc,heap     ] GC(17)  garbage-first heap total 
>> 131072K, used 64716K [0x00000000f8000000, 0x00000000f8100400, 
>> 0x0000000100000000)
>> [1,408s][trace  ][gc,heap     ] GC(17)   region size 1024K, 5 young 
>> (5120K), 5 survivors (5120K)
>> [1,408s][trace  ][gc,heap     ] GC(17)  Metaspace used 2967K, 
>> capacity 4562K, committed 4864K, reserved 1056768K
>> [1,408s][trace  ][gc,heap     ] GC(17)   class space used 277K, 
>> capacity 386K, committed 512K, reserved 1048576K
>> [1,408s][info   ][gc          ] GC(17) Pause Initial Mark (G1 
>> Evacuation Pause) 121M->63M(128M) (1,391s, 1,408s) 16,632ms
>> [1,408s][info   ][gc,cpu      ] GC(17) User=0,15s Sys=0,01s Real=0,02s
>>
>>
>> Thanks,
>> Bengt
>