Our application frequenlty undergoes 20-70 seconds of Young GC Pause time which leads to HTTP 504. This host has 30GB RAM and below is our startup flags. Any suggestions?
-Djava.awt.headless=true -XX:+AlwaysPreTouch -XX:+UseStringDeduplication -XX:+UseG1GC -XX:ParallelGCThreads=4 -XX:ConcGCThreads=4 -XX:InitiatingHeapOccupancyPercent=70 -XX:MaxMetaspaceSize=1024m -XX:MaxGCPauseMillis=500 -Xms16g -Xmx16g -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/mnt/tmp
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Hello Ysulai198,
MaxGCPauseMillis: This flag is a soft goal and may not be achieved if memory pressure is high. You might try removing it or adjusting it to a higher value. Sometime setting it too low can lead to more frequent GC activity. This is depending upon the need of the application.
Hello!
Most of your long pauses are triggered because of 'G1 Evacuation Puase'. This GC is triggered when copying live objects from one set of regions to another set of regions. When Young generation regions are only copied then Young GC is triggered. When both Young + Tenured regions are copied, Mixed GC is triggered.
Below are the potential solutiosn pointed by GCeasy to address this GC event:
1. Evacuation failure might happen because of over tuning. So eliminate all the memory related properties and keep only min and max heap and a realistic pause time goal (i.e. Use only -Xms, -Xmx and a pause time goal -XX:MaxGCPauseMillis). Remove any additional heap sizing such as -Xmn, -XX:NewSize, -XX:MaxNewSize, -XX:SurvivorRatio, etc.
2. If the problem still persists then increase JVM heap size (i.e. -Xmx).
3. If you can't increase the heap size and if you notice that the marking cycle is not starting early enough to reclaim the old generation then reduce -XX:InitiatingHeapOccupancyPercent. The default value is 45%. Reducing the value will start the marking cycle earlier. On the other hand, if the marking cycle is starting early and not reclaiming, increase the -XX:InitiatingHeapOccupancyPercent threshold above the default value.
4. You can also increase the value of the '-XX:ConcGCThreads' argument to increase the number of parallel marking threads. Increasing the concurrent marking threads will make garbage collection run fast.
5. Increase the value of the '-XX:G1ReservePercent' argument. Default value is 10%. It means the G1 garbage collector will try to keep 10% of memory free always. When you try to increase this value, GC will be triggered earlier, preventing the Evacuation pauses. Note: G1 GC caps this value at 50%.
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