RHEL 6 CPU load

[Blake Hudson]

- wrote the following on 11/20/2013 10:46 AM:
>>> Daniel, what do you see the load as? I see 4.6% CPU usage (100% possible
>>> - 95.4% idle).
>>
>> Wondering the same.  Don't consider 0.00 high load.  ;-)
>>
> :-) I guess I need to be a little better at explaining my self. It
> made perfect sense to me.
>
> I am talking about the named process which can run up to 180% during
> the day. When it is doing this the system still has very low load.
>
>>> I'm not sure which versions of BIND you were using on RHEL5, but the
>>> newer versions do tend to use more CPU usage (I'll assume due to new
>>> features, patches, etc in the BIND code).
>>>
>>> --Blake
>>>
>>> - wrote the following on 11/20/2013 9:37 AM:
>>>
>>> We recently upgraded one of our DNS servers to RHEL 6. The other two
>>> servers are running RHEL 5. The new system is showing much higher CPU
>>> load than the other two (RHEL 5 machines sit around 11-15%). I am not
>>> sure if this is related to the OS versions
>>> or something else. The build procedure for the new system is completely
>>> different than before which could also be the cause. Any ideas why this
>>> could be happening?
>>
>> Were the configure options the same when you built on 5.x vs 6.x? You can
>> see that with named -V.
>>
>> You mention a different build procedure -- do you mean named or OS? As a
>> first step I would focus on those differences. FWIW I have moved about 30
>> recursive resolvers with the highest iterative workload I've had the
>> privilege of managing to centos 6.x and had no ill effects so I don't
>> think it's simply the OS itself.
> Again, it made perfect sense to me.
>
> I am talking about the OS builds. Bind is compiled with the exact same
> options and the configs for this system is identical to the other
> slave server.
>
Depending on your OS and Bind settings, Bind may be performing IPv6/AAAA 
queries in parallel to IPv4/A queries. If IPv6 is disabled on your RHEL5 
server I suspect they may only be performing IPv4/A queries during 
recursion. You might check if this is, at least in part, responsible for 
the additional load.

> The issue for me is the HIGH CPU use for named. It is much lower for
> our RHEL 5 systems.
>
You didn't provide the same CPU information about your RHEL 5 builds as 
you did for your RHEL6 system, so I just responded about the information 
you did provide. Are these 24/32 core systems? Do the same number of 
named child processes run on both the RHEL5 and RHEL6 systems? I'm going 
to assume that you've already examined query load on the servers and 
found them similar.

--Blake