On this page you may modify the CONFIG.SYS settings which affect the OS/2 scheduler.
See "Processes and threads" for an introductory
explanation of what the scheduler does.
This help page will explain the different settings only and relate them to
the respective CONFIG.SYS commands.
If the information on this page regarding the different CONFIG.SYS settings is
not sufficient for you, you'll find additional explanations in the respective
chapters of the OS/2 Command Reference.
Press "Apply" to have the changes you've made written to the
CONFIG.SYS
file.
This will only change the lines which correspond to the settings on this
page. The lines corresponding to the other pages in the "OS/2 Kernel" object will
not be changed.
Please note that you will have to restart the computer to let the changes
take effect. A WPS restart does not suffice.
Press "Optimize" to have &xwp; propose you new settings according to
your system characteristics.
CONFIG.SYS will only be changed after you press "Apply" also.
Press "Default" to have the OS/2 default settings displayed on the notebook
page.
CONFIG.SYS will only be changed after you press "Apply" also.
The following fields are available:
- The "Current thread count" display shows you the total number of currently
running threads on your system. This display is continually updated: if you start a
new program you'll see that the thread count will increase.
- The "Maximum thread count" setting represents the THREADS
setting in CONFIG.SYS. Here you can determine how many threads OS/2 will be able to
handle altoghether. The maximum value is 4096. You can reduce the scheduler's overhead
and memory consumption by reducing this number.
According to IBM, OS/2 uses at least one memory page (4 KB) for each thread. That is,
if you specify 1024 threads, you have already used up 4 MB of memory.
If you don't use any network functions, a number of 256 should be sufficient.
Please note however that your system might crash
without further warning if you set this number too low. As a rule of thumb, you can
use the "Current thread count" displayed above and add 50% to that number.
This should give you enough security, because the majority of threads are started by the
system at bootup and most additional processes only use one or two threads each.
See the documentation in the
OS/2 Command Reference for details.
- The "Allow priority boost" setting represents the MAXWAIT
setting in CONFIG.SYS. This setting determines how many seconds a
thread that is ready to execute will get processor time although other
threads have a higher priority level. This setting only affects threads of the
"regular" priority class. The default value is three seconds, which I consider
an appropriate value for fast computers (Pentium or better). However, if you have
a slower system (486) you might experience a better system response if you lower this
setting to 2 or 1 second(s). By lowering this value, "background" threads will be given
more processor time, but at the cost of the "foreground" threads, which will be
interrupted more often. Experiment with this setting to find out which value suits
best your system. You should not however set a number larger than 3 seconds.
IBM has recommended that you should lower this setting if you use a lot of DOS/Windows
applications, but you should NOT lower it if you don't have much memory on your system
and therefore OS/2 works on the swap file a lot.
See the documentation in the
OS/2 Command Reference for details.
- The "Privilege foreground disk I/O" setting represents the
PRIORITY_DISK_IO setting in CONFIG.SYS.
If this setting is enabled
(which is the default),
the current foreground application will receive a
priority boost when its disk operation is complete. This applies to the first
time slice given to the thread after the disk operation is complete. After the
time slice, the state is reset for the thread and the priority boost is removed.
As a result, the foreground session will
have a better response time, at least when it is accessing the disks on your system.
You may want to disable this setting if you're frequently running software in the
background with heavy drive access, such as compilers.
See the documentation in the
OS/2 Command Reference for details.