G1 GC heap size is not bounded ?

[yao]

>
> All gcs have some memory overhead.  G1 might have more compared to other
> gcs.
>
> Can you share your data about what have increased?


In our case, we give 82G to JVM (via -Xmx) and the overall memory usage is
around 100G with G1. In contrast, the overall memory usage with CMS in
similar case is close to the number set via Xmx.



On Tue, Feb 18, 2014 at 10:45 PM, YU ZHANG <yu.zhang at oracle.com> wrote:

>  Shengzhe,
>
> All gcs have some memory overhead.  G1 might have more compared to other
> gcs.
>
> Can you share your data about what have increased?
>
> Thanks,
> Jenny
>
> On 2/18/2014 11:41 AM, yao wrote:
>
>  Hi All,
>
>  We've tracked our system memory usage for a week and found it seems stop
> increasing when reaching 100G. Besides RSet, it looks like G1 also
> allocates other data structure in off-heap manner. I have a follow up
> question, could we restrict the application memory usage equal to what we
> set in -Xmx when G1 is enabled ? Assume application itself doesn't allocate
> data in off-heap manner, that will make application memory usage more
> predictable.
>
>  Thanks
> Shengzhe
>
>
> On Mon, Feb 10, 2014 at 2:06 PM, yao <yaoshengzhe at gmail.com> wrote:
>
>>  Hi Ramki,
>>
>>  JDK version is  1.7.0_40
>>
>>  -Shengzhe
>>
>>
>> On Mon, Feb 10, 2014 at 1:36 PM, Srinivas Ramakrishna <ysr1729 at gmail.com>wrote:
>>
>>> Hi Shengzhe --
>>>
>>>  What's the version of JDK where you're running into this issue, and
>>> has the JVM had any STW full gc's because of mixed gc's not keeping up?
>>>
>>>  -- ramki
>>>
>>>
>>>  On Mon, Feb 10, 2014 at 11:39 AM, yao <yaoshengzhe at gmail.com> wrote:
>>>
>>>>   Hi All,
>>>>
>>>>  We've enabled G1 GC on our cluster for about 1 month and recently we
>>>> observed the heap size keeps growing (via RES column in top), though very
>>>> slowly. My question is, is there a way to bound heap size for G1 GC ?
>>>>
>>>> We set heap size to 82G
>>>>
>>>>
>>>> *-Xms83868m -Xmx83868m -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC *
>>>>  We found RES column is about 100G, (a few days ago it was about 93G)
>>>>
>>>>  *$ top*
>>>> PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>>>> 5757 hbase     20   0  104g *100g* 5240 S 271.3 79.6 177771:41 java
>>>>
>>>> From previous discussion, Thomas Schatzl pointed out this might be due
>>>> to large RSet. From below lines in gc log, we found RSet size is about
>>>> 10.5G. So we get Xmx + RSet = 82G + 10.5G = 92.5G, here you can see there
>>>> are still unexplained 7.5G data occupied our off-heap.
>>>>
>>>> RSet log:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> * Concurrent RS processed -1601420092 cards   Of 651507426 completed
>>>> buffers:      634241940 ( 97.3%) by conc RS threads.      17265486 (  2.7%)
>>>> by mutator threads.   Conc RS threads times(s)           0.00     0.00
>>>> 0.00     0.00     0.00     0.00     0.00     0.00     0.00     0.00
>>>> 0.00     0.00     0.00     0.00     0.00     0.00     0.00     0.00    \
>>>>  0.00     0.00     0.00     0.00     0.00     0.00   Total heap region rem
>>>> set sizes = 10980692K.  Max = 16182K.   Static structures = 563K,
>>>> free_lists = 78882K.     197990656 occupied cards represented.     Max size
>>>> region = 165:(O)[0x00007f0ce0000000,0x00007f0ce2000000,0x00007f0ce2000000],
>>>> size = 16183K, occupied = 3474K.     Did 0 coarsenings.*
>>>>
>>>>  Thanks
>>>>  -Shengzhe
>>>>
>>>>  _______________________________________________
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>>>> hotspot-gc-use at openjdk.java.net
>>>> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>>>>
>>>>
>>>
>>
>
>
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