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From "Xu Zhongxing" <xu_zhong_x...@163.com>
Subject Re:Re: High cpu usage when the cluster is idle
Date Sun, 25 Oct 2015 01:54:08 GMT
Thank you very much. I figured out the number of tables is the cause yesterday. Your analysis
confirmed that.






在2015年10月25 05时23分, "Graham Sanderson"<graham@vast.com>写道:

I would imagine you are running on fairly slow machines (given the CPU usage), but 2.0.12
and 2.1 use a fairly old version of the yammer/codehale metrics library.


It is waking up every 5 seconds, and updating Meters… there are a bunch of these Meters
per table (embedded in Timers), so your large 1500 table count is basically most of the problem.



AFAIK there is no way to turn the metrics off; they also power the JMX interfaces.


On Oct 24, 2015, at 7:54 AM, Xu Zhongxing <xu_zhong_xing@163.com> wrote:


The cassandra version is 2.0.12.  We have 1500 tables in the cluster of 6 nodes, with a total
2.5 billion rows.


在2015年10月24 20时52分, "Xu Zhongxing"<xu_zhong_xing@163.com>写道:




I saw an average 10% cpu usage on each node when the cassandra cluster has no load at all.
I checked which thread was using the cpu, and I got the following 2 metric threads each occupying
5% cpu.


jstack output:  


"metrics-meter-tick-thread-2" daemon prio=10 tic=...
  java.lang.Thread.State: WAITING (parking)
  at sum.misc.Unsafe.park(Native Method)
  -parking to wait for ...
  at ... (LockSupport.java:186)
  at ... (AbstractQueuedSynchronizer.java:2043)
...
at .. (Thread.java:745)


The other thread is the same.


Can someone give some clue to this problem? Thank you.

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