I've been experiencing an issue in a production application using G1 for quite some time over a handful of 1.8.0 builds. The application is relatively simple: it spends about 60s reading some parameters from files on disk, and then starts serving web requests which merge some input with those parameters, performs some computation and returns a result. We're aiming to keep max total request time (as seen by remote hosts) below 100 ms but from previous experience with parnew and cms (and g1 on previous projects, for that matter), I didn't anticipate this being a problem.
The symptoms are an ever-increasing time spent in evacuation pauses, and high parallel worker termination times stick out. With the recommended set of G1 settings (max heap size and pause time target), they increase sharply until I start seeing 500ms+ pause times and have to kill the JVM. I found some time ago that first forcing a bunch of full GCs with System.gc() at the phase (load -> serve) change and then forcing frequent concurrent cycles with -XX:InitiatingHeapOccupancyPercent=1 seems to mitigate the problem. I'd prefer to have to do neither, as the former makes redeployments very slow and the latter adds a couple of neighboring 40ms pauses for remark and cleanup pauses that aren't good for request time targets. I'm attaching a log file that details a short run, with the phase change at about 60s from start. After a few evacuation pauses, one lasts 160ms with nearly 100-120ms spent in parallel workers' 'termination'. After this, a concurrent cycle runs and everything goes back to normal. java params are at the top of the file. Generally this happens over a much longer period of time (and especially if I haven't given the low -XX:InitiatingHeapOccupancyPercent value) and over many different builds of 1.8.0. This was b101. It's running alone on a fairly hefty dual-socket Xeon box with 128GB of RAM on CentOS 7. I'd be more than happy to hear any ideas on what's going on here and how it could be fixed. Best, William
ooc_gc.log.gz
Description: GNU Zip compressed data
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