G1 GC heap size is not bounded ?

[yao]

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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>>>
>>>
>>
>
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