(5.6) Performance Tuning

How do I tweak OS/2 Warp for maximum performance?

For advice on tuning OS/2 Warp (including information on running games) please consult the documents located in the Information folder. Also, several tools have been developed to help tune OS/2 Warp for performance, notably:

Here are some basic steps you can take to improve the performance of your OS/2 Warp PC:

• Use FastLoad so that Windows applications start faster. Start the Win-OS/2 Setup program, located in your System Setup folder. There is a checkbox marked "FastLoad." Check this box to enable the FastLoad feature. When you start OS/2 Warp, a DOS session with Win-OS/2 will be started automatically and preloaded so that Windows applications will start faster. However, enabling FastLoad will increase the amount of time required to start OS/2 Warp.

  FastLoad will not provide any benefit if (a) you have enabled the "Separate session" feature for your Windows application(s); (b) your FastLoad session is set for a different mode than your Windows application(s). In other words, if your FastLoad session is set for Enhanced mode, the Windows applications you start from the OS/2 Warp desktop must also be set to Enhanced mode. You can adjust the FastLoad mode setting by using the Win-OS/2 settings button in the Win-OS/2 Setup notebook. The mode setting for a Windows application is controlled from the settings notebook for that application. If the mode settings are not identical, FastLoad can actually hamper performance.

• Adjust the disk cache size. Generally, OS/2 Warp can make better use of your PC's memory for applications, so you will usually want to keep the size of your disk cache modest. There are at least three types of disk caches available: FAT, HPFS, and CD-ROM. All are controlled by the CONFIG.SYS file. Normally OS/2 Warp will set the disk cache sizes correctly for your PC's amount of memory. However, you may wish to make changes, especially if you have added or removed memory from your PC.

  As a rule of thumb, the total size of your disk caches (combined) should be about 10% of your PC's available memory. For example, if you have a system with 12 MB of memory, then you can spare a little over a megabyte (1024K) for disk cache. The cache sizes for the three most popular OS/2 Warp file systems are controlled using the following lines in CONFIG.SYS:

  DISKCACHE=xxxx[,...]
  IFS=[...]HPFS.IFS /CACHE:yyyy [...]
  IFS=[...]CDFS.IFS /C:zz [...]

  (for FAT, HPFS, and CD-ROM, respectively). The "[...]" notation above indicates that additional, optional parameters are available for these lines. Replace "xxxx" or "yyyy" with the size of the cache you would like (in Kilobytes). For example, to set a cache size of 1 MB for the FAT file system:

  DISKCACHE=1024

  Replace "zz" with the size of the CD-ROM cache you wish to set, in 64K segments. For example, to set a cache size of 128K for the CD-ROM file system, use:

  IFS=[...]CDFS.IFS /C:2

  For more information on setting disk cache sizes, please refer to the online Command Reference.

• Relocate the OS/2 Warp swap file. For maximum performance, the swap file (controlled by the SWAPPATH line in CONFIG.SYS) should be located on the most used drive on the least used hard disk on your PC. Also, preallocating a larger swap file (8, 12, or even 16 MB) can increase performance. See your online Command Reference for details on SWAPPATH.
• Speed printing by dedicating IRQ 7. With OS/2 Warp, the default printing method is to poll the printer port (much like DOS). This method is compatible with a wide variety of PCs and printers, but sometimes printing speed suffers. For faster results, enable interrupt-driven printing. See (2.3) Printer Support for details.

Related information:

(1.3) DOS and Windows Compatibility
(2.3) Printer Support
(5.7) Measuring Performance and Memory Usage

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