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GC without Major GC  RSS feed

 
Nitin kumar Sharma
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HI All,

here is a strange thing i have recently observed, and I thought of getting inputs from Ranch member on same.

My application is running on Tomcat and java 1.6.0_43. i see that for young generation we have "PS Scavenge" and for old generation "PS Mark Sweep" configured. Also, the JVM size is 4GB with 896 MB configured for Young generation (-XX:MaxNewSize=896m & -XX:NewSize=896m).

Moreover, we are monitoring the JMX beans for PS Scavenge and PS Mark Sweep to analyze the GC pause and count of collections ..

Problem statement: I see that the used heap graph of my JVM will gradually been increasing till it reaches around 3.6GB and then suddenly the JVM will drop to a very low value (~ 200MB) .. It is obvious to assume that major/full GC is causing JVM to retract .. However, when i monitor PS Mark Sweep --> "Total Garbage Collection" counter, i see the value is 0 during heap drop and only PS Scavenge --> "Total Garbage Collection" had some positive numbers.

This is what I am not able to deduce that how come PS Scavenge(Young collection) can cause memory to fall from nearly the top limit(~3.6GB) to such a low .. PS scavenge can only clear up the memory in Young collection which is set to 896MB.
 
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