title: Understanding GC1 log file in java 11
body: <p>As part of the question in <a href="https://stackoverflow.com/questions/62897054/java-11-gc-logging">Java 11 GC logging</a> I am struggling to understand what the numbers actually mean.</p>
  <p>For example:</p>
  <pre><code>  [2020-07-14T10:01:14.791-0400][gc            ] GC(353) Pause Young (Normal) (G1 Evacuation Pause) 163M-&gt;16M(248M) 1.689ms
  [2020-07-14T10:01:14.790-0400][gc,heap       ] GC(353) Eden regions: 147-&gt;0(147)
  [2020-07-14T10:01:14.790-0400][gc,heap       ] GC(353) Survivor regions: 1-&gt;1(19)
  [2020-07-14T10:01:14.790-0400][gc,heap       ] GC(353) Old regions: 16-&gt;16
  [2020-07-14T10:01:14.790-0400][gc,heap       ] GC(353) Humongous regions: 1-&gt;1
  </code></pre>
  <p>I know that <code>147-&gt;0</code> is before/after collection, but what is the unit here and for the ones below? As I see it, is that the whole young generation is reduced from 163M to 16M , it also looks like this happens almost entirely within the Eden regions - so the objects already went out of scope before even moving to the survivor space?</p>