max_concurrent_checks=0 not working on 3.2.1 (maybe earlier versions, too)?

Max perldork at webwizarddesign.com
Mon Apr 19 13:53:18 CEST 2010


On Mon, Apr 19, 2010 at 5:12 AM, Andreas Ericsson <ae at op5.se> wrote:
>> This would indicate that max_concurrent_checks=0 is limiting it to
>> some number rather than using all the CPU possible, which sounds like
>> a bug.
>>
>
> Yes. I expect this has to do with the smart check interleave factor and
> wildly different check_interval variables. Nagios does something wrong
> there, but it's unusual enough (and mild enough) for most people that
> noone has bothered to correct it yet.

Will be very interested in seeing your results and hope you are able
to do great things with the process pooling and your investigation
into this.

As part of our mostly *black box* tuning for better performance, we
turn off the 'smart' intervals and we set check interleave factor to
always equal the number of hosts we are polling.  We also removed the
section of code where Nagios sleeps on non-runnable events and made
the sleep time between checks as small as we could with nanosleep
enabled.  we leave max concurrent checks at 0 as well.  With all that
in place and on a set up with a large % of ePN-based checks (~ 90% < 1
sec execution time according to nagiostats) and a NEB module
processing performance data we get a max of about 50 checks/second on
a dual quad core CPU host.  With DNX we saw that rise to about 85
checks/second but the version of DNX we tried was not honoring the
Nagios check schedule well (that was before all the patching work that
has been going on on the DNX project lately so might be better now).

- Max

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