I think we found why you're seeing lots of young gen-based GC pauses... :) 2011/9/30 Yang <teddyyyy...@gmail.com>: > why? > > I thought bigger young gen would allow more objects to die (become > non-reachable) before minor collection, so the minor collection cost > is low. particularly it would allow you to merge more updates and not > consume memory (since old objects are released on GC) > > bigger old gen would allow you to accumulate more rows into your > memtable, so you can avoid > later compaction cost. > > > if not giving it to heap, then it's a choice between os buffer and > cassandra row cache. I think row cache is definitely better since you > avoid the cost of serializing/deserializing; well this is assuming > that your access pattern is random though, otherwise OS cache has the > benefit of spacial locality (it loads blocks at once instead of a > single row). > > thanks > Yang > > 2011/9/30 Norman Maurer <norman.mau...@googlemail.com>: >> I would also not use such a big heap. I think most people will tell >> you that 12G -16G is max to use. >> >> Bye, >> Norman >> >> 2011/9/30 Yi Yang <i...@iyyang.com>: >>> It is meaningless to release such memory. The counting includes the data >>> you reached in the SSTable. Those data locates on your hard drive. So it is >>> not the RAM spaces you have actually used. >>> >>> -Y. >>> ------Original Message------ >>> From: Yang >>> To: user@cassandra.apache.org >>> ReplyTo: user@cassandra.apache.org >>> Subject: release mmap memory through jconsole? >>> Sent: Oct 1, 2011 12:40 AM >>> >>> I gave an -Xmx50G to my Cassandra java processs, now "top" shows its >>> virtual memory address space is 82G, is there >>> a way to release that memory through JMX ? >>> >>> Thanks >>> Yang >>> >>> 從我的 BlackBerry(R) 無線裝置 >> >
-- Jonathan Ellis Project Chair, Apache Cassandra co-founder of DataStax, the source for professional Cassandra support http://www.datastax.com
