FBSD 6.2 Xeon 2.4ghz CPU and high load

[DAve]

Chuck Swiger wrote:
> On May 9, 2008, at 8:54 AM, DAve wrote:
>> The issue I am seeing is that my server load, under the same traffic 
>> load, has increased 4 times or more. Where previously we saw a high 
>> load on the servers of 5 to 8, we are now seeing 14 to 17. Since the 
>> upgrade Sendmail has begun to timeout connections.
> 
> You should look more into the status of the various processes, and how 
> long it takes your mail scanning to process a message compared to 
> previously.  It might be the case that the config under 6.2 is allowing 
> more instances to run at once and is just barely nudging the system into 
> excessive paging.  Once that happens, performance drops and the system 
> load increases significantly.
> 
> Do a couple of "ps aux | head -20" every 5 minutes or so, and put that 
> data somewhere on a website, the process states will help give a better 
> picture of what's going on.
> 
> [ ... ]
>> bash-2.05b# top
>> last pid: 85205;  load averages: 12.89, 13.78, 
>> 14.66                                                              up 
>> 47+15:51:31  15:20:01
>> 126 processes: 12 running, 79 sleeping, 35 zombie
>> CPU states: 43.8% user,  0.0% nice,  6.3% system,  0.0% interrupt, 
>> 50.0% idle
>> Mem: 1008M Active, 582M Inact, 211M Wired, 78M Cache, 112M Buf, 122M Free
>> Swap: 4096M Total, 304M Used, 3792M Free, 7% Inuse
>>
>> I am suspicious of the kernel being the culprit because the system 
>> looks as if it is not working very hard, CPU load never shows above 
>> 50% idle. I found one thread which mentions that as an issue and 
>> offers a patch.
>>
>> http://lists.freebsd.org/pipermail/freebsd-bugs/2007-February/022526.html
>>
>> Currently I am running the SMP-GENERIC kernel and sysctl shows the 
>> following.
>>
>> hw.model: Intel(R) Xeon(TM) CPU 2.40GHz
>> machdep.hlt_logical_cpus: 0
>> machdep.hyperthreading_allowed: 0
>> kern.smp.cpus: 4
>> I see dev.cpu.0 through dev.cpu.3
>>
>> Can anyone offer a solution? Is this a known issue I can easily 
>> correct? At this point I am left with either rolling back to 4.11 or 
>> trying another OS.
> 
> It might be reasonable to try hyperthreading enabled, as your type of 
> load might be improved by it on....
> 

Funny that, enabling hyperthreading immediately dropped my load by half, 
I see CPU0, CPU1, CPU2, CPU3 now in top. I also see my CPU load 
reporting correctly as well. I see ranges from 10% idle to 80% idle, not 
locked at 50% and above.

That seems to have cured several ills. I will know more Monday at 8:30am 
when the business email traffic kicks in.

DAve


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