Hi, On Thu, 2017-07-13 at 08:51 -0700, Sundara Mohan M wrote: > Thanks for tuning link. > > I have 2 more JVM (31G heap with CMS GC) running on same machine but > gc logs never showed sys time > 1.4 only the JVM running with G1GC > shows very high sys time. > Another thing noticed is resident size is high compared to another > process which has CMS GC. > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND > 1438 test 20 0 42.0g 27g 34m S 283.8 21.7 5232:24 java > . >>> CMSGC > 619 test 20 0 42.0g 26g 34m S 105.0 21.3 5085:47 java > . >>> CMSGC > 600 test 20 0 43.4g 33g 33m S 4.3 26.9 361:54.17 java . > >>> G1GC > > > Is this something to do with G1GC region based allocation?
Yes, regions play into that, most likely remembered sets (used to do per-region evacuation, but can't tell without an NMT snapshots [0], and even then it is somewhat guessing). You can decrease remembered set memory usage by increasing heap region size (I think it is only 16m in your case, i.e. you are free to try 32m), or try to rebalance remembered set memory usage. The threads [1] and [2] give some insights on what to look for and what knobs to turn. JDK9 contains some improvements in the remembered set area. Also make sure to compare apples-to-apples. G1 has different heap sizing mechanisms, so it might just use a larger part of your provided Java heap memory. NMT can also show you that in addition to your logs. Thanks, Thomas [0] https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot /tooldescr007.html [1] http://mail.openjdk.java.net/pipermail/hotspot-gc-use/2017-February /002609.html [2] http://mail.openjdk.java.net/pipermail/hotspot-gc-use/2 017-March/002640.html _______________________________________________ hotspot-gc-use mailing list hotspot-gc-use@openjdk.java.net http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
