<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Thanks Charlie,<div><br></div><div>I only had a cursor look at the source and found the initial calculation but stopped there figuring someone here would know off the top of their heads. Didn't expect someone to splunk through the code so a big thanks for that.<div><br></div><div>Again, I'm struggling to think of a use case for this behaviour.</div><div><br></div><div>Regards,</div><div>Kirk</div><div><br><div><div>On 2012-10-19, at 8:56 PM, Charlie Hunt <<a href="mailto:chunt@salesforce.com">chunt@salesforce.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Don't mean to jump in front of Monica. :-/ But, she can confirm. ;-)<div><br></div><div>A quick look at the G1 source code suggests that if InitiatingHeapOccupancyPercent=0, the following will happen:</div><div>- the first minor GC will initiate a concurrent cycle implying that you'll see a young GC with an initial-mark in the GC log w/ +PrintGCDetails</div><div>- every minor GC there after, as long as there is not an active concurrent cycle, will initiate the start of a concurrent cycle</div><div>* So, in other words, concurrent cycles will run back to back. Remember that there needs to be a minor GC to initiate the concurrent cycle, i.e. the initial-mark. There is at least one caveat to that which I'll explain next. So, once a concurrent cycle complete, the next concurrent cycle will not start, until the next minor GC, or a humongous allocation occurs as described next.</div><div>- If there is a humongous object allocation, a concurrent cycle will be initiated (if InitiattingHeapOccupancyPercent=0). This is done before the humongous allocation is done.</div><div><br></div><div>charlie ...</div><div><br><div><div><div>On Oct 19, 2012, at 12:58 PM, Kirk Pepperdine wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><meta http-equiv="Content-Type" content="text/html charset=us-ascii"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">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 href="mailto:monica.beckwith@oracle.com">monica.beckwith@oracle.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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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>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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