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<font size="-1"><tt>Fabian,<br>
<br>
I am late to the party, still trying to figure out what is the
issue. From what I can follow the from<br>
<a class="moz-txt-link-freetext" href="https://groups.google.com/a/jclarity.com/forum/#!msg/friends/hsZiz6HTm9M/MbuttBioCgAJ">https://groups.google.com/a/jclarity.com/forum/#!msg/friends/hsZiz6HTm9M/MbuttBioCgAJ</a>,
the original complain is Ref Proc time is very long, and after
you added </tt></font><font size="-1"><tt>ParallelRefProcEnabled
and (maybe) other flags, it is better?<br>
<br>
I tried to look at the log gc.log.gz<br>
<a class="moz-txt-link-freetext" href="https://groups.google.com/a/jclarity.com/group/friends/attach/b13fb0b7fedd4/gc.log.gz?part=0.1&authuser=0&view=1">https://groups.google.com/a/jclarity.com/group/friends/attach/b13fb0b7fedd4/gc.log.gz?part=0.1&authuser=0&view=1</a><br>
In that log, -XX:+ParallelRefProcEnabled and refproc seems ok.
-XX:MaxHeapSize=4294967296, but the actual heap size is 1588m.
G1 might not expand the heap aggressively. You can try to run
with fixed Xms Xmx values.<br>
<br>
<br>
As for tenure distribution, yes, most of the objects(5-7m) die
young, but about 2m objects do not die, can live up to age
12-15, and get promoted. Though the old gen usage does not
increase after mixed gc, it is hard to tell if the mixed gc
cleaned those objects, or did compaction. Maybe with -Xms=4g
-Xmx=4g, the Eden size will increase, so is the survivor size,
but those 2m objects still get promoted. I think we need more
experiments to see if the ergonomic is doing the right thing.<br>
</tt></font>
<pre class="moz-signature" cols="72">Thanks,
Jenny</pre>
<div class="moz-cite-prefix">On 12/20/2015 5:27 AM, Fabian Lange
wrote:<br>
</div>
<blockquote
cite="mid:CAAViHO=pVfdpOriebf=mR88zMmOnW4=-CQaRyNf_uCYSxEOnow@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_quote">
<div dir="ltr">Hi,</div>
<div dir="ltr">(originall posted on adoption-discuss)<br>
<div>since a while I have been recommending and using G1GC
for JDK 8 applications.</div>
<div><br>
</div>
<div>This week I was looking at an application which should
be the ideal candidate.</div>
<div>It was given 4GB ram, has a steady memory usage of
about 1-2GB and during its work it generates only garbage.
It reads data from sockets, deserializes it, manipulates
it, serializes it and writes it out to sockets. It is
processing 100k to 500k of such requests per second.</div>
<div><br>
</div>
<div>With the default G1 settings the machine was very
loaded. The collection times were pretty long. It even ran
out of memory a few times because the GC could not catch
up.</div>
<div><br>
</div>
<div>When looking at the logs I was surprised to see
extremely small eden/young sizes. The old gen was really
big (like 3.5GB, but mostly empty) while G1 was churning
on 300MB young.</div>
<div><br>
</div>
<div>I raised the question on <a moz-do-not-send="true"
href="https://groups.google.com/a/jclarity.com/d/msg/friends/hsZiz6HTm9M/MbuttBioCgAJ"
target="_blank">https://groups.google.com/a/jclarity.com/d/msg/friends/hsZiz6HTm9M/MbuttBioCgAJ</a>
where Charlie Hunt was so kind to explain the reasons
behind the behaviour. It either did not make sense to me,
or I did not understand the explanation. </div>
<div><br>
</div>
<div>What I did is what I always did regardless of the
collector: I increased young space, knowing it contains
mostly garbage.</div>
<div>The overall behaviour of the JVM was much improved by
that.</div>
<div><br>
</div>
<div>I found it irritating, that according to Charlie, the
main reason for the small eden is the Pause Time Limit.
Because GC was not meeting its goal it reduced eden. While
I observed better results doing the opposite.</div>
<div><br>
</div>
<div>I also enabled -XX:+<span
style="font-family:Arial,Helvetica,sans-serif;font-size:13px">ParallelRefProcEnabled.</span></div>
<div><span
style="font-family:Arial,Helvetica,sans-serif;font-size:13px"><br>
</span></div>
<div><span
style="font-family:Arial,Helvetica,sans-serif;font-size:13px">Logs
are available from the above discussion, but I can send
them in separate mail if desired.</span></div>
<div><span
style="font-family:Arial,Helvetica,sans-serif;font-size:13px"><br>
</span></div>
<div><font face="Arial, Helvetica, sans-serif">As far as I
can tell the ergonomics are not working for me, and the
changes I need to do are counter intuitive. From other
discussions I learned that quite many people observed
better overall performance with raising the pause time
restriction.</font></div>
<div><font face="Arial, Helvetica, sans-serif"><br>
</font></div>
<div><font face="Arial, Helvetica, sans-serif">Is there
public information to why the current defaults are as
they are? How would feedback on these defaults work?</font></div>
<div><br>
</div>
<div>Best regards,</div>
<div>Fabian</div>
</div>
</div>
<br>
</div>
</blockquote>
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