ConcurrentMarkSweep GC超过1307ms

Question

如何在我的cassandra中调优CMS gc。我们看到这种情况每小时发生一次/ gc扫描在1307毫秒内接管了一秒的ConcurrentMarkSweep GC。CMS老一代: 377389368 -> 365877600；Par Eden Space: 588805072 -> 0；Par Survivor Space: 4718504 -> 0

我们在env文件中有如下的Heap设置。

MAX_HEAP_SIZE="8192M"
HEAP_NEWSIZE="800M" 

### CMS Settings

-XX:+UseParNewGC
-XX:+UseConcMarkSweepGC
-XX:+CMSParallelRemarkEnabled
-XX:SurvivorRatio=8
-XX:MaxTenuringThreshold=1
-XX:CMSInitiatingOccupancyFraction=75
-XX:+UseCMSInitiatingOccupancyOnly
-XX:CMSWaitDuration=10000
-XX:+CMSParallelInitialMarkEnabled
-XX:+CMSEdenChunksRecordAlways
# some JVMs will fill up their heap when accessed via JMX, see CASSANDRA-6541
-XX:+CMSClassUnloadingEnabled

Answer 1

没有足够的信息，但如果GC来自碎片，则减少XX:CMSInitiatingOccupancyFraction (55)可能会有所帮助。