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Andrei Mikhaltsov
Asked: 2012-11-29 07:06:50 +0800 CST

High CPU usage on mongodb server when idle?

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I'm getting strange usage numbers on MongoDB server when it is in almost idle state: http://pastebin.com/cKVyGMts (no queries) DB size is about 3.3 Gb.

I can see in mongodb.log that snapshotthread is eating too much CPU:

Wed Nov 28 19:02:14 [snapshotthread] cpu: elapsed:4000 writelock: 0% Wed Nov 28 19:02:18 [snapshotthread] cpu: elapsed:4000 writelock: 0% Wed Nov 28 19:02:22 [snapshotthread] cpu: elapsed:4000 writelock: 0% Wed Nov 28 19:02:26 [snapshotthread] cpu: elapsed:4000 writelock: 0%

And data from top confirms it: http://pastebin.com/d57ybpBJ (iotop shows that there are no high disk activity present).

I'm running high-cpu instance on EC2, mongo confing and startup information is here: http://pastebin.com/YZyyq0gc.

How I can disable snapshotting or what can cause such a high CPU usage?

mongodb

1 Answers

  1. According to JIRA some changes where made to memory allocation algorithm in version 2.2.0, which possibly could fix this issue.

    MongoDB high CPU usage, low disk IO, very slow response

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