frequent full GC: why?

[Y.S.Ramakrishna at Sun.COM]

Please add -XX:+DisableExplicitGC just in case, unbeknownst to you,
some third-party library (or the jdk libraries) are calling system gc.

-- ramki

On 05/19/09 10:12, Anuj Lal wrote:
>  
> 
> Jdk version 1.5.0_16rev9
> 
> What can the cause of full gc back to back?.
> 
> We are seeing frequent full GC even though enough space there in old 
> space as well as in perm space ?.
> 
> When new space fills up I expect only new gc but not FULL GC.
> 
>  
> 
> Old space is only 126 MB filled ( out of 194MB)
> 
> Permspace is only 129MB out of 215 ( max perm space is 256mb)
> 
>  
> 
> These is our setting
> 
> -Xms2410m -server -XX:CMSInitiatingOccupancyFraction=75 Xmx2410m 
> -XX:NewSize=512M -XX:MaxNewSize=512M -XX:MaxTenuringThreshold=6 
> -XX:SurvivorRatio=5 -XX:TargetSurvivorRatio=80  -XX:MaxPermSize=256M 
> -XX:ThreadStackSize=256 -verbose:gc -XX:+PrintGCTimeStamps 
> -XX:+PrintClassHistogram -XX:+UseConcMarkSweepGC -XX:+UseParNewGC 
> -XX:+CMSParallelRemarkEnabled -XX:+UseCMSCompactAtFullCollection 
> -XX:CMSFullGCsBeforeCompaction=0 -XX:+HandlePromotionFailure 
>  -XX:+UseCMSInitiatingOccupancyOnly -XX:CMSMarkStackSize=32M 
> -XX:CodeCacheMinimumFreeSpace=2M -XX:ReservedCodeCacheSize=64M - 
> -XX:CMSMaxAbortablePrecleanTime=1 -XX:+PrintGCDetails -XX:+PrintHeapAtGC 
> -XX:+PrintTenuringDistribution –
> 
>  
> 
>  
> 
> 1071256.659: [Full GC {Heap before gc invocations=4293:
> 
>  par new generation   total 449408K, used 380965K [0x4f800000, 
> 0x6f800000, 0x6f800000)
> 
>   eden space 374528K,  99% used [0x4f800000, 0x66517448, 0x665c0000)
> 
>   from space 74880K,   9% used [0x665c0000, 0x66cb2318, 0x6aee0000)
> 
>   to   space 74880K,   0% used [0x6aee0000, 0x6aee0000, 0x6f800000)
> 
>  concurrent mark-sweep generation total 1943552K, used 141477K 
> [0x6f800000, 0xe6200000, 0xe6400000)
> 
>  concurrent-mark-sweep perm gen total 215832K, used 129513K [0xe6400000, 
> 0xf36c6000, 0xf6400000)
> 
> 1071256.661: [CMS: 141477K->126065K(1943552K), 3.9483474 secs] 
> 522443K->126065K(2392960K), [CMS Perm : 129513K->129487K(215832K)]Heap 
> after gc invocations=4294:
> 
>  par new generation   total 449408K, used 0K [0x4f800000, 0x6f800000, 
> 0x6f800000)
> 
>   eden space 374528K,   0% used [0x4f800000, 0x4f800000, 0x665c0000)
> 
>   from space 74880K,   0% used [0x665c0000, 0x665c0000, 0x6aee0000)
> 
>   to   space 74880K,   0% used [0x6aee0000, 0x6aee0000, 0x6f800000)
> 
>  concurrent mark-sweep generation total 1943552K, used 126065K 
> [0x6f800000, 0xe6200000, 0xe6400000)
> 
>  concurrent-mark-sweep perm gen total 215832K, used 129487K [0xe6400000, 
> 0xf36c6000, 0xf6400000)
> 
> }
> 
> , 3.9511002 secs]
> 
> 1071289.014: [Full GC {Heap before gc invocations=4294:
> 
>  par new generation   total 449408K, used 129843K [0x4f800000, 
> 0x6f800000, 0x6f800000)
> 
>   eden space 374528K,  34% used [0x4f800000, 0x576ccd88, 0x665c0000)
> 
>   from space 74880K,   0% used [0x665c0000, 0x665c0000, 0x6aee0000)
> 
>   to   space 74880K,   0% used [0x6aee0000, 0x6aee0000, 0x6f800000)
> 
>  concurrent mark-sweep generation total 1943552K, used 126065K 
> [0x6f800000, 0xe6200000, 0xe6400000)
> 
>  concurrent-mark-sweep perm gen total 215832K, used 129496K [0xe6400000, 
> 0xf36c6000, 0xf6400000)
> 
> 1071289.016: [CMS[Unloading class 
> sun.reflect.GeneratedSerializationConstructorAccessor1251]
> 
> [Unloading class sun.reflect.GeneratedMethodAccessor3111]
> 
> : 126065K->123793K(1943552K), 4.6073158 secs] 
> 255908K->123793K(2392960K), [CMS Perm : 129496K->129483K(215832K)]Heap 
> after gc invocations=4295:
> 
>  par new generation   total 449408K, used 0K [0x4f800000, 0x6f800000, 
> 0x6f800000)
> 
>   eden space 374528K,   0% used [0x4f800000, 0x4f800000, 0x665c0000)
> 
>   from space 74880K,   0% used [0x665c0000, 0x665c0000, 0x6aee0000)
> 
>   to   space 74880K,   0% used [0x6aee0000, 0x6aee0000, 0x6f800000)
> 
>  concurrent mark-sweep generation total 1943552K, used 123793K 
> [0x6f800000, 0xe6200000, 0xe6400000)
> 
>  concurrent-mark-sweep perm gen total 215832K, used 129483K [0xe6400000, 
> 0xf36c6000, 0xf6400000)
> 
> }
> 
> , 4.6100803 secs]
>