High CPU usage with RC-4



  • Two weeks ago, I upgraded my pfSense installation from 1.2-RC2 to RC4.  Since then, I've noticed periods of very high CPU usage, and I often (several times per day) see these messages in the log:

    root: Resetting slbd due to high cpu usage: 104%

    This is directly related to installing RC4.  In the graph below, the increased number of processes and the spikes in CPU usage began immediately after I installed RC4.

    pfSense is running on a 2.4 GHz Core 2 Duo, with 4 gigabytes of RAM.  I have a triple WAN setup:  3 10-gigabyte lines being load balanced into a single LAN.  Granted, I'm hitting it pretty hard with a web crawler, but I was hitting RC2 just as hard with the same crawler.

    I did, for a brief period, turn the DNS Forwarder on after installing RC4, but that's been off now for a few days, and the CPU usage spikes remain.

    Any idea what's causing this?  Is it something I should be worried about?




  • This is the same slbd problem that's been around from day one, you apparently never hit it until your last upgrade.

    If you install the uniprocessor kernel this will go away. That's the only work around that will be available in 1.2. slbd will be replaced entirely in 1.3 for this reason amongst others.



  • Is there a HOW TO on switching kernels?  If not, maybe a hint on where to get a little more info?

    I a little hesitant to change things, as it appears to be working.  Even though those CPU spikes are a little bit of a concern.  And I'm really not excited about having to reconfigure everything.  Can I change kernels without having to reconfigure my pfSense settings?



  • You should back up your pfSense settings anyway.
    The resulting config.xml has all the infos you need to re-apply all settings to a fresh install.
    IIRC, it currently doesn't back up certificates and RRD graph data, though.



  • @jmischel:

    Is there a HOW TO on switching kernels?  If not, maybe a hint on where to get a little more info?

    I a little hesitant to change things, as it appears to be working.  Even though those CPU spikes are a little bit of a concern.  And I'm really not excited about having to reconfigure everything.  Can I change kernels without having to reconfigure my pfSense settings?

    Yes you can.


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