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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hi all<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>A customer of ours is experiencing instances whereby the Sun
JDK 1.4.2_16 on Windows goes through many Full GC<font color=navy><span
style='color:navy'>s</span></font> for no good reason. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The Sun JDK parameters used are: </span></font><font size=2
face=Arial><span lang=EN-AU style='font-size:10.0pt;font-family:Arial'>-Xms1280m
-Xmx1280m -XX:NewSize=500m -XX:MaxNewSize=500m -XX:PermSize=150m
-XX:MaxPermSize=150m -server -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'>I have enclosed a snippet of the garbage collection
logs with minor GC before and after (ProblematicFullGC.zip).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'>From timestamp 21928.044 to 21958.226 + 5 seconds aka
35 seconds, the JVM goes through 8 Full GCs with hardly any time in between.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'>To the users, the JVM is frozen. <font color=navy><span
style='color:navy'>T</span></font>he JVM needs to get restarted to get back to
a good state.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'>The most surprising is that the new generation is
almost empty (1 or 2 MB max used out of 460MB) in all but the first Full GC and
that there is a lot of free space in the tenured generation (more than 400MB).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'>Our thinking is that the JVM may be triggering a Full
GC because of the “Young Generation Guarantee”.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'>If such is the case, the behaviour is not consistent across
platforms: we have run a similar load test in house with Sun JDK 1.4.2_16 on
Linux with the identical parameters (“</span></font><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>-server -Xms1280m
-Xmx1280m -XX:NewSize=500m -XX:MaxNewSize=500m -XX:PermSize=150m
-XX:MaxPermSize=150m -XX:+PrintGCDetails -XX:+PrintHeapAtGC
-XX:+PrintGCTimeStamps -verbose:gc”</span></font><font size=2 face=Arial><span
lang=EN-AU style='font-size:10.0pt;font-family:Arial'>. In that case, the Full
GCs occur very normally though the tenured space is much fuller (140-180MB free
only). A snippet of the GC logs is enclosed at OKGC.zip. It shows several Full
GCs with a healthy dose of minor GC in between.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'>So far, we have recommended to the customer that they
use a smaller New Generation, as this may make it less likely to get closer to
the “Young Generation Guarantee” threshold. Nevertheless, as the
math is not there for that “Young Generation Guarantee”, we want to
dig further into this.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'>Thanks in advance for any help.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-AU style='font-size:
10.0pt;font-family:Arial'>Alex Aisinzon<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Arial><span lang=EN-AU
style='font-size:10.0pt;font-family:Arial;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Arial><span lang=EN-AU
style='font-size:10.0pt;font-family:Arial;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color="#1f497d" face="Times New Roman"><span
lang=EN-AU style='font-size:12.0pt;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color="#1f497d" face="Times New Roman"><span
lang=EN-AU style='font-size:12.0pt;color:#1F497D'> </span></font><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'><o:p></o:p></span></font></p>
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