[CentOS] Strange performance issues under CentOS 5.1

Alfred von Campe alfred at von-campe.com
Wed Feb 13 13:59:40 UTC 2008


On Feb 12, 2008, at 21:57, William L. Maltby wrote:

> Check BIOS settings? For memory, CAS etc. the same? Disk hardware the
> same and specified identically?

Pretty much all the same.  They are standard Lenovo desktops, with a  
3.4 GHz Core 2 Duo and 3 GB of memory (the BIOS doesn't let the OS  
address more than 3 GB).

> Presumming that nothing is found there, install system accounting
> packages and run some SAR reports. You may see a clue in them.

I will try that next.

> Any "tweaks" on the old system you forgot to apply on the new?  
> Elevator,
> buffer flush interval changes, etc?

Nope, it's a vanilla kickstart install.  I am using the same scripts  
(with only slight variations) to build both the 4.x and 5.x systems.   
I didn't do anything to "tune" the 4.x systems.  That's one of the  
things I like about CentOS (and RHEL for that matter): they just work  
out of the box.  A build (make/gcc) is typically CPU bound.  I don't  
understand how it can get only 11% of the CPU.  That's unheard of.

> Any other noticeable things on there that may cause it? Presume the
> slowdown is caused by a process that you are not looking at. "Hangs"
> while some other process is waiting or tying up the CPU. Try running
> top.

There is nothing else running on the systems at the time.  I have  
lots of terminal windows open on the 4.x system, but I am ssh'ed into  
the 5.x system and nobody else is logged in.  If anything, the 4.x  
system should be slower since there are many more things running on it.
>
> I notice an execve shows on the new one that is not in the old. One  
> says
> "hmmm....".

The execve is in the other as well, just a few lines further down  
(i.e., it didn't make the cut when I did the "head strace.log").

> What does swapon -s show?

CentOS 4.6:
     Filename                                Type            Size     
Used    Priority
     /dev/mapper/VolGroup00-LogVol00         partition       4095992  
210592  -1

CentOS 5.1:
     Filename                                Type            Size     
Used    Priority
     /dev/mapper/VolGroup00-LogVol00         partition       3047416  
120     -1

> Is the system "seeing" the same amount of memory "available" or have
> BIOS settings in one reduced available?

CentOS 4.6:
     MemTotal:      3113612 kB
     MemFree:         24868 kB
     Buffers:         23164 kB
     Cached:        2428508 kB
     SwapCached:     136108 kB
     Active:        1685808 kB
     Inactive:      1257004 kB
     HighTotal:     2226560 kB
     HighFree:         1088 kB
     LowTotal:       887052 kB

CentOS 5.1:
     MemTotal:      3114452 kB
     MemFree:       2722528 kB
     Buffers:         84592 kB
     Cached:         174804 kB
     SwapCached:          0 kB
     Active:         187084 kB
     Inactive:       137220 kB
     HighTotal:     2226560 kB
     HighFree:      1972860 kB
     LowTotal:       887892 kB

> If all new equipment on the new one, open her up and reseat all
> connections, PCI cards and mem sticks. Make sure all power connectors
> are well seated to MB and drives.

I will double check that.  I may also try to install 4.6 on the HW  
that is currently running 5.1 and see if there is a problem.  With my  
kickstart scripts I can have the system up and running in less than  
30 minutes.  That is probably the best next step to rule out any HW  
issues.  I'll do that as soon as I get into the office.

> Front side bus and memory speeds set the same in BIOS?

Should be.

> That's all I can think of that may be even remotely related ATM

Thanks for all the excellent suggestions, Bill.

Alfred




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