title: Large 'sync' value for ParallelGCFailedAllocation
body: <p>Sometimes I see long pauses in my gc.log</p>
  <blockquote>
  <p>2014-07-18T18:42:26.137+0400: 7846.980: [GC [PSYoungGen: 86267K-&gt;10032K(87744K)] 251198K-175254K(272512K), 0.0066190 secs] [Times: user=0.08 sys=0.00, real=0.01 secs]</p>
  <p>Total time for which application threads were stopped: <strong>0.6394170</strong> seconds</p>
  <p>Total time for which application threads were stopped: 0.0014570 seconds</p>
  </blockquote>
  <p>But these pauses don't affect GC time and CPU usage time.</p>
  <p>Safepoint statistics (+XX:PrintSafePointStatistics):</p>
  <blockquote>
  <p>vmop [threads: total initially_running wait_to_block] [time: spin block sync cleanup vmop] page_trap_count
  7846.348: ParallelGCFailedAllocation [ 370 0 2 ] [ 0 0 630 1 7 ] 0</p>
  </blockquote>
  <p>(sync time = 630ms) What does 'sync' mean in this context?</p>