MongoDB idling at 15-20% CPU usage

[lazymanc]

I'm experiencing an issue where mongodb consumes 15-20% CPU constantly when idle. This is especially inconvenient when trying to develop on a laptop as it drains the battery a lot more quickly than necessary.

Details:

• Host: Mac OS X 10.7.4 (mid 2011 macbook air 13")
• Guest: Ubuntu 12.04 server (64-bit) configured with 512mb ram / 8gb sata disk.
• Mongodb installed via 10gen repo as described here: ​http://docs.mongodb.org/manual/tutorial/install-mongodb-on-debian-or-ubuntu-linux/
• mongodb monitored using top command

The mongod process idles at 15-20% cpu usage on the ubuntu guest, even when no connections are active. I have converted the same VM image and run it under Parallels and the issue goes away (mongodb idling at 0-1% cpu). Others have mongodb running under vmware and xen and cannot reproduce the issue, so it appears to be specific to virtualbox.

[lazymanc]

screenshot of top

[vasily Levchenko]

Could you please attach the log?

[Frank Mehnert]

No response, closing.

[Froggy01]

Hi All,

I have exactly the same behaviour with MongoDB and VirtualBox here.

The Ubuntu 12.04 VM was exported from a KVM machine hosted on CentOs (qemu-img convert -O vdi Ubuntu.qcow2 Ubuntu.vdi) and imported into VirtualBox on Win 7 as a new machine with existing image.

Enverything works normally except the mongo process consuming 10-20% CPU even when no mongo request is performed.

The mongodb log show no difference beteen KVM/VirtualBox...

Calling strace show the same series of 'select' calls on both nodes:

select(13, [11 12], NULL, NULL, {0, 5127}) = 0 (Timeout)
select(13, [11 12], NULL, NULL, {0, 10000}) = 0 (Timeout)
select(13, [11 12], NULL, NULL, {0, 10000}) = 0 (Timeout)
select(13, [11 12], NULL, NULL, {0, 10000}) = 0 (Timeout)
...

@Hachiman/Frank, what log were you requesting ?