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Hi Kirk,<br>
<br>
Apologies that I'm a bit late to this conversation.<br>
<br>
An IHOP value of 0 pretty much means you'll be doing almost continuous
concurrent marking cycles - interspaced with an an occasional young GC
and some mixed GCs.<br>
<br>
There are two places where we check whether we should initiate a
marking cycle. One in when we allocate a humongous object (an object
that is larger than 1/2 of a region and may span multiple regions): if
the occupany of the heap plus the size of the object being allocated
will go over the IHOP, we schedule a young collection with an initial
mark piggy backed on top of it to start a marking cycle. The other
place is at the end of a young GC, if the heap occupancy is more than
the IHOP we indicate that the next young collection will have an
initial mark piggy-backed, starting the marking cycle.<br>
<br>
I use an IHOP of 0, 1, 5, and 10 to stress concurrent marking while
testing. :)<br>
<br>
I'm almost certain that this is not what Soumit intended.<br>
<br>
Regards,<br>
<br>
JohnC<br>
<br>
On 10/19/12 10:58, Kirk Pepperdine wrote:
<blockquote cite="mid:1A6AB65C-E2AB-483C-9533-17BA577BA693@kodewerk.com"
type="cite">
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Hi Monica,
<div><br>
</div>
<div>Can you comment on what a value of 0 means?</div>
<div><br>
</div>
<div>Regards,</div>
<div>Kirk</div>
<div><br>
<div>
<div>On 2012-10-19, at 2:55 PM, Monica Beckwith <<a
moz-do-not-send="true" href="mailto:monica.beckwith@oracle.com">monica.beckwith@oracle.com</a>>
wrote:</div>
<br class="Apple-interchange-newline">
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<div bgcolor="#FFFFFF" text="#000000"> Couple of quick observations
and questions - <br>
<ol>
<li>G1 is officially supported in 7u4. (There are numerous
performance improvements that I recommend updating to the latest jdk7
update, if possible)</li>
<li>What do you mean by old gen collection? Are you talking about
MixedGCs?</li>
<li>Instead of setting InitiatingHeapOccupancyPercent to zero,
have you tried resizing your young generation?</li>
<ol>
<li>I see the NewRatio, but that fixes the nursery to 640,
instead have you tried with a lower (than the min default) of nursery
using the NewSize option?</li>
</ol>
</ol>
<p>-Monica<br>
</p>
<br>
<br>
On 10/19/2012 12:13 AM, csewhiz wrote:
<blockquote
cite="mid:13a7770622f.3368361147554026191.2919233442948217281@zoho.com"
type="cite">
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<div
style="font-size: 10pt; font-family: Verdana,Arial,Helvetica,sans-serif;">
<div>Hello All,</div>
<div> Sorry for posting this question in this mailing list. I am
unable to find any answer for this. I am trying to tune our application
for G1GC as we need very small pauses Below 500msec. </div>
<div> But the problem is when we are runing with G1GC (under jdk
6_u37) Old generation of garbage collection only happening when it is
reaching the Max GC size I noticed on jdk 6U 37 if max heap size is 1GB
then it is close to 1sec 2GB close to 2 sec pauses. </div>
<div> </div>
<div> Is there any parameter to force the old gc happening
regularly. </div>
<div> </div>
<div>I am trying following setting, </div>
<div> </div>
<div>-Xms1280M -Xmx1280M -XX:+UseG1GC -XX:MaxTenuringThreshold=15
-XX:SurvivorRatio=8 -XX:NewRatio=1 -XX:GCPauseIntervalMillis=7500
-XX:MaxGCPauseMillis=500 -XX:InitiatingHeapOccupancyPercent=0
-XX:ParallelGCThreads=7 -XX:ConcGCThreads=7 </div>
<div> </div>
<div>If anyone can give insight on how full GC is triggred
internals will be of great help.</div>
<div> </div>
<div>PS: I have tried without any option for G1 but not of much
help hence .. this one trying to be agressive ? but of not much help.</div>
<div> </div>
<div> </div>
<div>Regards,</div>
<div>Soumit<br>
<br>
</div>
</div>
</blockquote>
<br>
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size="2">Monica Beckwith | Java Performance Engineer<br>
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512 401 1274</a> <br>
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