Full GC again...

Question

Hi,
I can not figure out what makes VM to run Full GC from time to time like in the listing below...
Any ideas ?
thanks,
Alex
JRE 1.5.0_06, Linux 2.6.9
java -Xms300M -Xmx300M -XX:ThreadStackSize=100 -Xss100K -server -XX:NewSize=80M -XX:MaxNewSize=80M -XX:SurvivorRatio=2 -XX:TargetSurvivorRatio=80 -XX:PermSize=8M -XX:+DisableExplicitGC -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 -verbose:gc -Xloggc:gc.log -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC
2069.493: [Full GC {Heap before gc invocations=79:
def new generation   total 61440K, used 59230K [0x9be40000, 0xa0e40000, 0xa0e40000)
  eden space 40960K,  99% used [0x9be40000, 0x9e637258, 0x9e640000)
  from space 20480K,  89% used [0x9fa40000, 0xa0c20618, 0xa0e40000)
  to   space 20480K,   0% used [0x9e640000, 0x9e640000, 0x9fa40000)
tenured generation   total 225280K, used 26314K [0xa0e40000, 0xaea40000, 0xaea40000)
   the space 225280K,  11% used [0xa0e40000, 0xa27f2a10, 0xa27f2c00, 0xaea40000)
compacting perm gen  total 8192K, used 5258K [0xaea40000, 0xaf240000, 0xb2a40000)
   the space 8192K,  64% used [0xaea40000, 0xaef62bb0, 0xaef62c00, 0xaf240000)
No shared spaces configured.
2069.493: [DefNew: 59230K->13381K(61440K), 0.0525370 secs] 85544K->44677K(286720K)Heap after gc invocations=80:
def new generation total 61440K, used 13381K [0x9be40000, 0xa0e40000, 0xa0e40000)
eden space 40960K, 0% used [0x9be40000, 0x9be40000, 0x9e640000)
from space 20480K, 65% used [0x9e640000, 0x9f351700, 0x9fa40000)
to space 20480K, 0% used [0x9fa40000, 0x9fa40000, 0xa0e40000)
tenured generation total 225280K, used 31295K [0xa0e40000, 0xaea40000, 0xaea40000)
the space 225280K, 13% used [0xa0e40000, 0xa2ccfe90, 0xa2cd0000, 0xaea40000)
compacting perm gen total 8192K, used 5258K [0xaea40000, 0xaf240000, 0xb2a40000)
the space 8192K, 64% used [0xaea40000, 0xaef62bb0, 0xaef62c00, 0xaf240000)
No shared spaces configured.
, 0.0530170 secs]
2469.687: [Full GC {Heap before gc invocations=106:
def new generation   total 61440K, used 55607K [0x9be40000, 0xa0e40000, 0xa0e40000)
  eden space 40960K,  99% used [0x9be40000, 0x9e63d9c8, 0x9e640000)
  from space 20480K,  71% used [0x9e640000, 0x9f4903f0, 0x9fa40000)
  to   space 20480K,   0% used [0x9fa40000, 0x9fa40000, 0xa0e40000)
tenured generation   total 225280K, used 37794K [0xa0e40000, 0xaea40000, 0xaea40000)
   the space 225280K,  16% used [0xa0e40000, 0xa3328868, 0xa3328a00, 0xaea40000)
compacting perm gen  total 8192K, used 5269K [0xaea40000, 0xaf240000, 0xb2a40000)
   the space 8192K,  64% used [0xaea40000, 0xaef657c0, 0xaef65800, 0xaf240000)
No shared spaces configured.
2469.687: [DefNew: 55607K->17641K(61440K), 0.0471880 secs] 93401K->55435K(286720K)Heap after gc invocations=107:
def new generation total 61440K, used 17641K [0x9be40000, 0xa0e40000, 0xa0e40000)
eden space 40960K, 0% used [0x9be40000, 0x9be40000, 0x9e640000)
from space 20480K, 86% used [0x9fa40000, 0xa0b7a748, 0xa0e40000)
to space 20480K, 0% used [0x9e640000, 0x9e640000, 0x9fa40000)
tenured generation total 225280K, used 37794K [0xa0e40000, 0xaea40000, 0xaea40000)
the space 225280K, 16% used [0xa0e40000, 0xa3328868, 0xa3328a00, 0xaea40000)
compacting perm gen total 8192K, used 5269K [0xaea40000, 0xaf240000, 0xb2a40000)
the space 8192K, 64% used [0xaea40000, 0xaef657c0, 0xaef65800, 0xaf240000)
No shared spaces configured.
, 0.0476750 secs]

Answer 1

... I was wondering where the bug was - in printing wrong string "Full GC" or reporting wrong time taken (too small) ..
The former: the time reported is correct; the labelling incorrect.
just in case, here is the log (I have decreased NewGen to 64M, this is not relevant):
2396.504: [GC 2396.504: [DefNew: 47224K->9605K(49152K), 0.0400940 secs] 112418K->78033K(290816K), 0.0404530 secs]
2402.309: [GC 2402.309: [DefNew: 41801K->13500K(49152K), 0.0457490 secs] 110229K->81928K(290816K), 0.0461060 secs]
2406.942: [GC 2406.942: [DefNew: 45077K->9378K(49152K), 0.0394620 secs] 113505K->80513K(290816K), 0.0398060 secs]
2411.607: [Full GC 2411.607: [DefNew: 42146K->11418K(49152K), 0.0349480 secs] 113344K->82616K(290816K), 0.0352890 secs]
2416.128: [GC 2416.128: [DefNew: 44158K->9744K(49152K), 0.0317540 secs] 115356K->80942K(290816K), 0.0321090 secs]
2431.779: [GC 2431.779: [DefNew: 42468K->9302K(49152K), 0.0271300 secs] 113666K->80501K(290816K), 0.0274990 secs]
2460.115: [GC 2460.115: [DefNew: 42032K->11956K(49152K), 0.0336600 secs] 113230K->83154K(290816K), 0.0340210 secs]
3092.676: [GC 3092.676: [DefNew: 39567K->8249K(49152K), 0.0244080 secs] 120895K->89577K(290816K), 0.0248020 secs]
3124.416: [GC 3124.416: [DefNew: 41017K->5334K(49152K), 0.0171250 secs] 122345K->86662K(290816K), 0.0174840 secs]
3142.484: [GC 3142.484: [DefNew: 38076K->5809K(49152K), 0.0190090 secs] 119404K->87137K(290816K), 0.0193580 secs]
3180.263: [Full GC 3180.263: [DefNew: 37247K->11496K(49152K), 0.0325830 secs] 120244K->94493K(290816K), 0.0329220 secs]
3195.934: [GC 3195.935: [DefNew: 44261K->8529K(49152K), 0.0259260 secs] 127258K->91525K(290816K), 0.0262790 secs]
3215.063: [GC 3215.063: [DefNew: 41285K->9952K(49152K), 0.0305630 secs] 124282K->92949K(290816K), 0.0309070 secs]
3240.325: [GC 3240.325: [DefNew: 42681K->10632K(49152K), 0.0302890 secs] 125678K->93629K(290816K), 0.0306430 secs]
5162.202: [GC 5162.202: [DefNew: 40081K->10374K(49152K), 0.0303690 secs] 142830K->113123K(290816K), 0.0307280 secs]
5204.101: [GC 5204.101: [DefNew: 43142K->8355K(49152K), 0.0247200 secs] 145891K->111104K(290816K), 0.0251820 secs]
5249.579: [GC 5249.580: [DefNew: 41070K->10846K(49152K), 0.0303930 secs] 143820K->113596K(290816K), 0.0307730 secs]
5297.293: [Full GC 5297.293: [DefNew: 43613K->9367K(49152K), 0.0268350 secs] 146506K->112260K(290816K), 0.0272170 secs]
5339.380: [GC 5339.381: [DefNew: 42126K->9040K(49152K), 0.0257950 secs] 145019K->111934K(290816K), 0.0262130 secs]
6547.097: [GC 6547.097: [DefNew: 41793K->12224K(49152K), 0.0351110 secs] 160746K->131177K(290816K), 0.0354630 secs]
6565.279: [GC 6565.279: [DefNew: 44990K->13642K(49152K), 0.0392770 secs] 163943K->132595K(290816K), 0.0396340 secs]
6592.978: [GC 6592.978: [DefNew: 46399K->9603K(49152K), 0.0341560 secs] 165352K->130663K(290816K), 0.0345430 secs]
6604.130: [GC 6604.130: [DefNew: 42357K->11840K(49152K), 0.0339120 secs] 163417K->132900K(290816K), 0.0342860 secs]
6614.478: [Full GC 6614.478: [DefNew: 44559K->11806K(49152K), 0.0341900 secs] 165938K->133185K(290816K), 0.0345730 secs]
6632.990: [GC 6632.990: [DefNew: 44553K->10977K(49152K), 0.0304230 secs] 165932K->132356K(290816K), 0.0308000 secs]
6672.913: [GC 6672.913: [DefNew: 43745K->11242K(49152K), 0.0333820 secs] 165124K->133029K(290816K), 0.0337680 secs]
10494.398: [GC 10494.398: [DefNew: 42791K->16384K(49152K), 0.0704750 secs] 238852K->214976K(290816K), 0.0710270 secs]
10500.641: [GC 10500.641: [DefNew: 49132K->49132K(49152K), 0.0000380 secs]10500.641: [Tenured: 198592K->67274K(241664K), 0.2976110 secs] 247724K->67274K(290816K), 0.2982150 secs]
10520.521: [GC 10520.522: [DefNew: 32265K->5236K(49152K), 0.0251580 secs] 99539K->72511K(290816K), 0.0256880 secs]
10537.788: [GC 10537.788: [DefNew: 37999K->8494K(49152K), 0.0326010 secs] 105273K->75768K(290816K), 0.0331660 secs]
11226.210: [GC 11226.211: [DefNew: 44215K->12969K(49152K), 0.0404320 secs] 140029K->108783K(290816K), 0.0409650 secs]
11247.099: [GC 11247.100: [DefNew: 45685K->12518K(49152K), 0.0393710 secs] 141499K->108332K(290816K), 0.0398880 secs]
11276.615: [Full GC 11276.616: [DefNew: 45286K->12032K(49152K), 0.0401870 secs] 141190K->107936K(290816K), 0.0406980 secs]
11294.301: [GC 11294.302: [DefNew: 44798K->11197K(49152K), 0.0378100 secs] 140702K->107102K(290816K), 0.0383170 secs]
11307.024: [GC 11307.024: [DefNew: 43926K->9435K(49152K), 0.0340290 secs] 139830K->106229K(290816K), 0.0345590 secs]