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.

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.


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