System information

4 System Analysis and Tuning Guide
scription. If you plan to tune your Web server for faster delivery of static pages, for
example, it makes a difference whether you need to generally improve the speed or
whether it only needs to be improved at peak times.
Furthermore, make sure you can apply a measurement to your problem, otherwise you
will not be able to control if the tuning was a success or not. You should always be
able to compare “before” and “after”.
1.2 Rule Out Common Problems
A performance problem often is caused by network or hardware problems, bugs, or
configuration issues. Make sure to rule out problems such as the ones listed below be-
fore attempting to tune your system:
• Check /var/log/warn and /var/log/messages for unusual entries.
• Check (using top or ps) whether a certain process misbehaves by eating up unusu-
al amounts of CPU time or memory.
• Check for network problems by inspecting /proc/net/dev.
• In case of I/O problems with physical disks, make sure it is not caused by hardware
problems (check the disk with the smartmontools) or by a full disk.
• Ensure that background jobs are scheduled to be carried out in times the server load
is low. Those jobs should also run with low priority (set via nice).
• If the machine runs several services using the same resources, consider moving ser-
vices to another server.
• Last, make sure your software is up-to-date.
1.3 Finding the Bottleneck
Finding the bottleneck very often is the hardest part when tuning a system. SUSE Lin-
ux Enterprise Server offers a lot of tools helping you with this task. See PartII, “Sys-
tem Monitoring” (page7) for detailed information on general system monitor-
ing applications and log file analysis. If the problem requires a long-time in-depth