title: G1 Garbage Collector spending a majority of time in Ref Proc
body: <p>I'm new to the G1 Garbage collection, but I have a heap with a Max of 26G, initial size 10G, and it's current size is 26G with 15G used. </p>
  
  <p>I have GC logging turned on with the following arguments:</p>
  
  <pre><code>-XX:+PrintGC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -XX:+PrintTenuringDistribution -verbose:gc -Xloggc:
  </code></pre>
  
  <p>When I check out my garbage collection garbage collection log, I notice that my <code>Ref Proc</code> seems to take the longest.  I have <code>-XX:MaxGCPauseMillis=1000</code> specified and my GC time is close to this, but it still seems like, to me, <code>Ref Proc</code> is running for a long time. I was wondering if there was a way of reducing this time? </p>
  
  <p>Excerpt of my GC log:</p>
  
  <pre><code>[GC pause (young)
  Desired survivor size 335544320 bytes, new threshold 15 (max 15)
  - age   1:   18542272 bytes,   18542272 total
  - age   2:    1752016 bytes,   20294288 total
  - age   3:    1083928 bytes,   21378216 total
  - age   4:    1078592 bytes,   22456808 total
  - age   5:     854640 bytes,   23311448 total
  - age   6:     549048 bytes,   23860496 total
  - age   7:    1372744 bytes,   25233240 total
  - age   8:     623048 bytes,   25856288 total
  - age   9:     909984 bytes,   26766272 total
  - age  10:     930072 bytes,   27696344 total
  - age  11:     928088 bytes,   28624432 total
  - age  12:    1053440 bytes,   29677872 total
  - age  13:     553512 bytes,   30231384 total
  - age  14:     787592 bytes,   31018976 total
  - age  15:     985216 bytes,   32004192 total
  , 1.22150400 secs]
     [Parallel Time: 176.4 ms]
        [GC Worker Start (ms):  209376973.5  209376973.6  209376973.6  209376973.6  209376973.7  209376973.7  209376973.7  209376973.8  209376973.8  209376973.8  209376973.8  209376973.9  209376973.9  209376974.0  209376974.0  209376974.0  209376974.0  209376974.1  209376974.1  209376974.1  209376974.1  209376974.2  209376974.2
         Avg: 209376973.9, Min: 209376973.5, Max: 209376974.2, Diff:   0.7]
        [Ext Root Scanning (ms):  2.2  2.0  2.2  1.5  36.8  2.2  3.6  1.6  1.6  1.6  1.7  2.2  1.7  1.5  1.5  1.5  1.5  1.8  1.7  1.6  1.3  1.6  1.7
         Avg:   3.3, Min:   1.3, Max:  36.8, Diff:  35.5]
        [Update RS (ms):  13.4  14.0  13.2  14.1  0.0  13.2  12.0  13.7  14.1  13.7  13.7  13.0  13.6  13.7  14.0  13.8  13.7  13.2  13.5  13.8  13.8  13.3  13.3
         Avg:  13.0, Min:   0.0, Max:  14.1, Diff:  14.1]
           [Processed Buffers : 8 4 16 6 0 11 10 9 14 8 8 11 15 5 7 7 13 16 9 6 12 7 13
            Sum: 215, Avg: 9, Min: 0, Max: 16, Diff: 16]
        [Scan RS (ms):  0.3  0.0  0.4  0.0  0.2  0.3  0.2  0.3  0.0  0.3  0.3  0.3  0.3  0.2  0.0  0.3  0.3  0.4  0.2  0.0  0.3  0.3  0.3
         Avg:   0.2, Min:   0.0, Max:   0.4, Diff:   0.3]
        [Object Copy (ms):  151.2  150.7  151.0  150.9  130.3  151.0  150.9  150.3  151.0  150.5  151.5  150.5  151.2  151.6  151.5  151.0  151.4  150.8  150.2  150.3  151.2  150.2  151.3
         Avg: 150.0, Min: 130.3, Max: 151.6, Diff:  21.2]
        [Termination (ms):  4.5  4.8  4.7  4.9  4.2  4.7  4.7  5.4  4.6  5.2  4.2  5.2  4.5  4.1  4.1  4.6  4.2  4.8  5.5  5.2  4.5  5.5  4.4
         Avg:   4.7, Min:   4.1, Max:   5.5, Diff:   1.4]
           [Termination Attempts : 2171 2328 2294 2328 2003 2294 2274 2497 2232 2498 1970 2481 2191 2035 2006 2287 2007 2320 2640 2554 2243 2532 2216
            Sum: 52401, Avg: 2278, Min: 1970, Max: 2640, Diff: 670]
        [GC Worker End (ms):  209377145.9  209377145.2  209377145.8  209377145.5  209377145.3  209377145.8  209377145.9  209377145.7  209377145.8  209377145.2  209377145.4  209377145.6  209377145.2  209377145.2  209377145.2  209377145.8  209377145.9  209377145.4  209377145.7  209377145.6  209377145.2  209377145.6  209377146.0
         Avg: 209377145.6, Min: 209377145.2, Max: 209377146.0, Diff:   0.9]
        [GC Worker (ms):  172.4  171.6  172.2  171.9  171.7  172.1  172.2  171.9  172.0  171.3  171.5  171.8  171.3  171.2  171.2  171.9  171.9  171.4  171.6  171.5  171.0  171.4  171.8
         Avg: 171.7, Min: 171.0, Max: 172.4, Diff:   1.3]
        [GC Worker Other (ms):  4.8  4.8  4.8  4.9  4.9  4.9  4.9  5.0  5.0  5.1  5.1  5.1  5.2  5.2  5.2  5.2  5.3  5.3  5.3  5.4  5.4  5.4  5.5
         Avg:   5.1, Min:   4.8, Max:   5.5, Diff:   0.7]
     [Clear CT:   1.9 ms]
     [Other: 1043.2 ms]
        [Choose CSet:   0.1 ms]
        [Ref Proc: 1029.7 ms]
        [Ref Enq:   5.5 ms]
        [Free CSet:   6.4 ms]
     [Eden: 4660M(4660M)-&gt;0B(4680M) Survivors: 460M-&gt;440M Heap: 15178M(25600M)-&gt;10501M(25600M)]
   [Times: user=4.98 sys=0.00, real=1.22 secs]
  </code></pre>