[oclug] Kernel locks,
delays on querying /proc/pid/stat and qlogic driver
bart-oclug at jukie.net
Sat Apr 17 19:04:31 EDT 2004
* Christo Kutrovsky <kutrovsky+oclug at pythian.com> [040417 00:56]:
> We have a system with 8 CPUs (XEON with HT=on so 16 visible) and 18gb
> of RAM...
Allow me to recover my jaw from the floor.
> ... The system is running kernel 2.4.9-e.37summit and it's primarily
> purpose is to run an Oracle database.
Do you know if Oracle will run on 2.6 based kernel? I know that a
higher "responsiveness feeling" can be obtained from an upgrade to 2.6.
Not sure if it will help in this instance.
It may be worth a try.
> It is a datawarehouse style system, so lots of IO going to a SAN with
> 700Gb+ of storage used.
What kind of SAN connection? SCSI, SCSI over IP, NFS, something else?
> The code was rather simple and I took a guess and assumed that
> "read_lock" is where the most time is spend, since that's the only
> /proc/pid/stat extra function call "stat" has over all other files.
It could also be stolen from you in the context-switch between
user-space and kernel and back out. IIRC, the kernel will attempt to
run outstanding post-interrupt (bottom halves & tasklets) processing at
this time. If you have poorly behaving drivers the processing of these
outstanding events could be done with a spin-lock and prevent other
things from happening... although this alone would not explain the other
7 CPUs not running your 'ls'.
> So I concluded that the qlogic driver (i2x00-v6.06.60-fo) must be
> causing the problems as this is the only thing that is different on
> the system.
This is a good conclusion.
> Any hints are welcome. Including pure theories.
Cannot offer much other then suggesting you use a newer kernel (even a
newer 2.4 kernel if you are not willing to try a 2.6), and talk to
RedHat. You are paying for support with the advanced server, no?
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