my young-gen pauses are fine, they are generally below 0.1 seconds, for my application that's fine for me :)
(I do see pauses of other nature, much longer (20seconds), some due to GC (full GC), which I'm still investigating) 2011/9/30 Jonathan Ellis <jbel...@gmail.com>: > 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 >
