[PLUG] help with /proc/cpuinfo

[Aaron Burt]

On 2019-04-24 17:40, VY wrote:
> We have several machines and they are all supposedly identical Intel 
> Xeon
> machines. 4 CPUs each and identical Linux version.
> One of the machines are reporting VERY high load consistently.
> They are all running identical applications and I don't see any 
> difference
> in load.

Classic problem.  Fun and very educational to solve.

Some clarifying questions:

1. By "4 CPUs" do you mean 4 separate CPU dies/packages, 4 cores in a 
single package on the mobo or 2 cores with hyperthreading?  Or are these 
VMs from AWS or something?

2. By "VERY high load", what do you mean? loadavg?  What values on 
normal vs affected system?  Is it spiky (the three 1m/5m/15m loadavgs 
are very different) or consistent (the three loadavg values are about 
the same)?

3. How does total CPU usage break out in "top" - user, system, 
interrupt, iowait etc.?

4. If you hit "1" in "top", is it affecting all cores equally or just 
one core?

5. Is this affecting application performance, and if so what effects are 
you seeing?

6. Have you rebooted the affected system?

7. Have you done a "chkrootkit" or other security/intrusion check on the 
affected system?


> However, when I look at /proc/cpuinfo, this "very high load" box is 
> saying:
>    apicid : 25
>   initial apicid : 25
> All the other machines are reporting 4 for this number.

Interesting.  Is it the same number for all 4 cores on each machine?  I 
don't know if the APIC is on the die on your setup, but there's usually 
only a few of those so 25 sounds like a weird number.  Maybe the funny 
one is running your kernel inside some virtualization layer?

Learning experiences abound,
   Aaron