<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
</head>
<body bgcolor="#FFFFFF" text="#000000">
Hi all,<br>
<br>
Could I have some reviews for this change?<br>
<br>
Concurrent gc timer and tracer are mainly used from concurrent mark
thread except when abort happens. This abort results in a race
condition between VM thread and concurrent mark thread.<br>
So I propose to do timer and tracer related works only from
concurrent mark thread.<br>
<br>
Measurements are changed like below:<br>
<table border="1" width="100%" cellpadding="2" cellspacing="2">
<tbody>
<tr>
<td valign="top"><br>
</td>
<td valign="top">Current<br>
</td>
<td valign="top">Proposal<br>
</td>
</tr>
<tr>
<td valign="top">Start timer and tracer<br>
</td>
<td valign="top">When Young Initial Mark GC starts from VM
thread<br>
</td>
<td valign="top">When actually starts concurrent cycle from
concurrent mark thread<br>
</td>
</tr>
<tr>
<td valign="top">End timer and tracer<br>
</td>
<td valign="top">1. At the end of concurrent cycle<br>
2. When abort happens</td>
<td valign="top">At the end of concurrent cycle<br>
<br>
* I think this will be okay as even though we abort, we
continue working for concurrent stuffs to finish concurrent
work cycle. And we were just not measuring them.</td>
</tr>
<tr>
<td valign="top">Heap summary (before-gc)<br>
</td>
<td valign="top">At the beginning of Young Initial Mark GC.<br>
But concurrent mark thread is not working at that time.</td>
<td valign="top">At the start of concurrent cycle.</td>
</tr>
<tr>
<td valign="top">Heap summary (after-gc)<br>
</td>
<td valign="top">1. When abort happens before cleanup: sent
when abort happens.<br>
2. When abort happens after cleanup or normal case(w/o
abort): sent at the end of cleanup.</td>
<td valign="top">At the end of concurrent cycle which means it
will include all minor clearing after 'Pause Cleanup'.</td>
</tr>
</tbody>
</table>
<br>
This proposal also includes related changes like below:<br>
1. Removed the patch for JDK-8149834(race between VM thread and
concurrent mark thread for concurrent gc timer): 8149834 was making
related functions atomically while this proposal is changing not to
happen that race.<br>
2. Removed G1CollectorState::_concurrent_cycle_started: no longer
needed as related logics are running from concurrent mark thread.<br>
<br>
Currently 'total concurrent time' is not same as 'sum of concurrent
phases' and the reason is that the concurrent timer is started when
young initial mark gc happens. Secondly, concurrent mark thread is
not counting the time for waiting VMThread to finish VM
operation(SuspendibleThreadSet). <br>
I am planning to enhance this after '8151614: Improve logging in
concurrent mark code' is pushed.<br>
<br>
CR: <a class="moz-txt-link-freetext" href="https://bugs.openjdk.java.net/browse/JDK-8151085">https://bugs.openjdk.java.net/browse/JDK-8151085</a><br>
Webrev: <a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~sangheki/8151085/webrev.00">http://cr.openjdk.java.net/~sangheki/8151085/webrev.00</a><br>
Testing: JPRT, RBT(hotspot_all, testlist: running now), local
reproducer for JDK-8149834<br>
<br>
Thanks,<br>
Sangheon<br>
</body>
</html>