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HP-UX System Administrator's Guide: Routine Management Tasks: HP-UX 11i Version 3 > Chapter 6 Managing System Performance

Performance Bottlenecks


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A system may perform slowly or sluggishly for a variety of reasons, and you may need to do considerable investigation to determine the source of bottlenecks on a given system. You need to consider the interrelationships between the different components of the system, not just its individual components. Start with the tools described under “Measuring Performance”.

Once you have isolated a performance problem and you decide how to address it, change only one thing at a time. If you change more than one thing, you will not know which change helped performance. It’s also possible that one change will improve performance while another makes it worse, but you won’t know that unless you implement them separately and measure performance in between.

The following shows some possible system bottlenecks:

CPU Bottlenecks:

  • Many background processes running at a high priority consuming a lot of CPU time, or a “runaway” process. If response time is unacceptable, lower the priority of some processes, and kill any unwanted processes.

Memory Bottlenecks:

  • high deactivations

  • high paging activity

  • little or no free memory available

  • high CPU usage in System mode

Disk Bottlenecks:

  • high disk activity

  • high idle CPU time waiting for I/O requests to finish

  • long disk queues

    NOTE: Put your most frequently accessed information on your fastest disks, and distribute the workload evenly among identical, mounted disks so as to prevent overload on a disk while another is under-utilized. This can often be accomplished by moving swap areas and heavily accessed file systems off the root disk, or by using disk striping, LVM, and/or disk mirroring to spread I/Os over multiple disks. See also “Checking Disk Load with sar and iostat”.

Network Bottlenecks:

  • Excessive demand on an NFS server.

  • LAN bandwidth limitations

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