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From André Warnier ...@ice-sa.com>
Subject Java +GC question
Date Sun, 24 Nov 2013 12:29:58 GMT
Hi.
This is not a pure Tomcat question, just related. I hope that the Java expertise present 
on this list might allow a quick rough answer.

OS : Debian 3.2.46-1~bpo60+1 i686 GNU/Linux

Java info :
# java -server -version
java version "1.6.0_26"
Java(TM) SE Runtime Environment (build 1.6.0_26-b03)
Java HotSpot(TM) Server VM (build 20.1-b02, mixed mode)

System memory usage info:
# free
              total       used       free     shared    buffers     cached
Mem:       3114844    2947360     167484          0      17768    2372508
-/+ buffers/cache:     557084    2557760
Swap:      5859324      39360    5819964

Question:

One of our Linux systems is running a background permanent Java process, started with the

following command-line options :

./java -server -Xms128M -Xmx128M -Xloggc:/home/xxx/xxx_gc.log -XX:+PrintGC 
-XX:+PrintGCTimeStamps ... -jar jar-file.jar

My question is just : to a Java expert eye, does the following GC trace look "normal" , or

"pathological", or in-between ?
(and accessorily, how does one interpret the leading timestamp ?
seconds.milliseconds since JVM start ?)


Sample contents of the GC logfile :

...
3484797.072: [Full GC 1607K->753K(126720K), 0.0415410 secs]
3507300.493: [Full GC 6651K->799K(126720K), 0.0239830 secs]
3508197.401: [Full GC 1507K->839K(126720K), 0.0247090 secs]
3508703.684: [GC 35782K->1485K(126720K), 0.0014440 secs]
3509098.112: [Full GC 9245K->888K(126720K), 0.0603780 secs]
3509997.732: [Full GC 1596K->753K(126720K), 0.0231020 secs]
3510897.991: [Full GC 1461K->794K(126720K), 0.0389760 secs]
3511797.605: [Full GC 1501K->834K(126720K), 0.0230580 secs]
3512697.608: [Full GC 18190K->890K(126720K), 0.0263780 secs]
3513597.620: [Full GC 1598K->753K(126720K), 0.0469200 secs]
3514497.557: [Full GC 1460K->793K(126720K), 0.0382910 secs]
3515397.128: [Full GC 1501K->834K(126720K), 0.0232420 secs]
3516298.110: [Full GC 33765K->906K(126720K), 0.0270450 secs]
3517197.288: [Full GC 1468K->753K(126720K), 0.0451560 secs]
3518098.189: [Full GC 34605K->826K(126720K), 0.0526920 secs]
3518997.666: [Full GC 1338K->866K(126720K), 0.0232330 secs]
3519897.722: [Full GC 2859K->908K(126720K), 0.0237370 secs]
3520617.399: [GC 35852K->2220K(126720K), 0.0029720 secs]
3520797.213: [Full GC 7599K->760K(126720K), 0.0496770 secs]
3521698.220: [Full GC 1431K->801K(126720K), 0.0260610 secs]
3522597.525: [Full GC 1508K->841K(126720K), 0.0230380 secs]
3523497.230: [Full GC 1549K->881K(126720K), 0.0351840 secs]
3524397.728: [Full GC 1590K->753K(126720K), 0.0439350 secs]
3525297.762: [Full GC 1461K->794K(126720K), 0.0357500 secs]
3526197.104: [Full GC 1501K->834K(126720K), 0.0231210 secs]
3527098.242: [Full GC 1542K->874K(126720K), 0.0277570 secs]
3527997.312: [Full GC 1582K->754K(126720K), 0.0455090 secs]
3528898.282: [Full GC 26344K->818K(126720K), 0.0307250 secs]
3529797.050: [Full GC 1381K->858K(126720K), 0.0261330 secs]
3530698.086: [Full GC 1567K->899K(126720K), 0.0243030 secs]
3531597.998: [Full GC 1606K->754K(126720K), 0.0250980 secs]
3532498.797: [Full GC 1462K->794K(126720K), 0.0335000 secs]
3533398.598: [Full GC 1502K->834K(126720K), 0.0229160 secs]
...

Thanks


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