Hello, I am currently benchmarking different in-process caching libraries. In some benchmark scenarios I found very "odd" results when using the G1 garbage collector. In a particular benchmark scenario the performance (as measured in ops/s of the particular benchmark) drops to about 30% when compared to CMS, typically I expect (and observe) only a performance degradation to around 80% of the performance with CMS.
In the blog post is a little bit more background of what I am doing: https://cruftex.net/2017/03/28/The-6-Memory-Metrics-You-Should-Track-in-Your-Java-Benchmarks.html For the particular scenario I have made the following observations: - Java 8 VM 25.131-b11: VmRSS, as reported by Linux, grows to 4.2 GB - Java 8 VM 25.131-b11: Average benchmark performance throughput is 2098524 ops/s - Java 8 VM 25.131-b11: Throughput is quite steady - Java 9 WM 9-EA+165: VmRSS, as reported by Linux, grows to 6.3 GB - Java 9 WM 9-EA+165: Average benchmark performance throughput is 566699 ops/s - Java 9 WM 9-EA+165: Throughput has big variations and the tendency to decrease - Java 9 WM 9-EA+165: Profiling shows that 44.19% of CPU cycles is spent in OtherRegionsTable::add_reference (for Java 8 G1 it is similar) And less quantified: - With Java 8 G1 it seems more worse - Scenarios with smaller heap/cache sizes don't show the high performance drop when comparing CMS and G1 - Java 9 WM 9-EA+165 with the options -XX:+UseParallelGC -XX: +UseParallelOldGC, seems to have 50% performance of Java 8 and higher memory consumption (What are the correct parameters to restore the old default behavior?) - The overall GC activity and time spend for GC is quite low To reproduce the measurements: Hardware: Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz, 1x4GB, 1x16GB @ DDR3 1600MHz, 2 cores with hyperthreading enabled OS/Kernel: Linux version 4.4.0-72-generic (buildd@lcy01-17) (gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4) ) #93-Ubuntu SMP Fri Mar 31 14:07:41 UTC 2017 git clone https://github.com/headissue/cache2k-benchmark.git cd cache2k-benchmark git checkout d68d7608f18ed6c5a10671f6dd3c48f76afdf0a8 mvn -DskipTests package java -jar jmh-suite/target/benchmarks.jar \\.RandomSequenceBenchmark -jvmArgs -server\ -Xmx20G\ -XX:BiasedLockingStartupDelay=0\ -verbose:gc\ -XX: +PrintGCDetails -f 1 -wi 0 -i 10 -r 20s -t 4 -prof org.cache2k.benchmark.jmh.LinuxVmProfiler -p cacheFactory=org.cache2k.benchmark.Cache2kFactory -rf json -rff result.json When not on Linux, strip "-prof org.cache2k.benchmark.jmh.LinuxVmProfiler". I have the feeling this could be worth a closer look. If there are any questions or things I can help with, let me know. I would be interested to know whether there is something that I can change in the code to avoid triggering this behavior. Best, Jens -- "Everything superfluous is wrong!" // Jens Wilke - headissue GmbH - Germany \// https://headissue.com _______________________________________________ hotspot-gc-use mailing list hotspot-gc-use@openjdk.java.net http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
