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<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>Hi,<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>I’m new to this list and I have a few questions
about tuning my young generation gc. <o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>I have chosen to use the CMS garbage collector
because my application is a relatively large reporting server that has a web
front end and therefore needs to have minimal pauses. <o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>I am using java 1.6.0_16 64-bit on redhat 5.2 intel
8x3GHz and 64GB ram.<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>The machine is dedicated to this JVM.<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>My steady-state was calculated as follows:<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><font face=Arial size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Arial'><span style='mso-list:Ignore'>-<font face="Times New Roman" size=1><span style='font:7.0pt "Times New Roman"'>
</span></font></span></span></font><![endif]><font face=Arial size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Arial'>A typical number of users
logged in and viewed several reports<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><font face=Arial size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Arial'><span style='mso-list:Ignore'>-<font face="Times New Roman" size=1><span style='font:7.0pt "Times New Roman"'>
</span></font></span></span></font><![endif]><font face=Arial size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Arial'>Stopped user actions and
performed a manual full GC<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><font face=Arial size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Arial'><span style='mso-list:Ignore'>-<font face="Times New Roman" size=1><span style='font:7.0pt "Times New Roman"'>
</span></font></span></span></font><![endif]><font face=Arial size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Arial'>Look at the amount of
heap used and take that number as the steady-state memory requirement<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>In this case my heap usage was ~10GB. In order
to handle variance or spikes I sized my old generation at 15-20GB.<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>I sized my young generation at 32-42GB and used
survivor ratios of 1, 2, 3 and 6.<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>My goal is to maximize throughput and minimize
pauses. I’m willing to sacrifice ram to increase speed.<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>I have attached several of my many gc logs. The
file gc_48G.txt is just using CMS without any other tuning, and the results are
much worse than what I have been able to accomplish with other settings.
The best results are in the files gc_52G_20Gold_32Gyoung_2sr.txt and
gc_57G_15Gold_42Gyoung_1sr.txt.<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>The problem is that some of the pauses are just too
long.<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>Is there a way to reduce the pause time any more than
I have it now?<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>Am I heading in the right direction? I ask
because the default settings are so different than what I have been heading
towards.<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>The best reference I have found on what good gc logs
look like come from brief examples presented at JavaOne this year by Tony
Printezis and Charlie Hunt. But I don’t seem to be able to get logs
that resemble their tenuring patterns.<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>I think I have a lot of medium-lived objects instead
of nice short-lived ones.<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>Are there any good practices for apps with objects
like this?<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>Thanks,<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>Jeff<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
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