G1 GC heap size is not bounded ?

[yao]

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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