[CentOS] Kernel 2.6.32-573.22.1.el6.x86_64, higher than usual load

Fri Apr 8 13:32:52 UTC 2016
Johnny Hughes <johnny at centos.org>

On 04/08/2016 06:50 AM, Johnny Carlsen wrote:
> Hi,
> After switching to the 2.6.32-573.22.1.el6.x86_64 kernel (CentOS 6) a few weeks ago I have noticed that my servers are now reporting a much higher idle load.
> The servers are being monitored with Zabbix, and there is a clear difference between the older kernel 2.6.32-573.12.1 and the newer 2.6.32-573.12.1.
> I can see the problem on both physical and virtual servers.
> You can see the Load Average chart here from one of our servers:
> http://imgur.com/U1eihMX
> The server is pretty much idle all the time, but the load average increased from 0.001 to 0.300 when updated to the new kernel.
> Is anyone else seeing the same behavior?

This is one of the fixes listed on the errata page:

"Due to prematurely decremented calc_load_task, the calculated load
average was off by up to the number of CPUs in the machine. As a
consequence, job scheduling worked improperly causing a drop in the
system performance. This update keeps the delta of the CPU going into
NO_HZ idle separately, and folds the pending idle delta into the global
active countwhile correctly aging the averages for the idle-duration
when leaving NO_HZ mode. Now, job scheduling works correctly, ensuring
balanced CPU load. (BZ#1300349)"


No idea if that is impacting the load shown on your machine .. maybe
someone has some ideas.

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