On Thursday 15 March 2007 17:13, James Knott wrote:
> Windows has never been able to multi-task as well as OS/2 or Linux.
And this is why...
... notes from NT tutorial ...
------------------------------------------ start
The major role of the kernel in Windows NT is to dispatch and schedule
threads. A thread is a code segment belonging to a particular process. Each
thread is assigned a priority number from 0 to 31. The kernel dispatches
threads to run on available processors based on their priority numbers. The
kernel then allows the threads to execute for a particular amount of time
before preempting them and allowing another process to run.
NOTE:
Sometimes you see it written that the kernel schedules processes. While
this is **not technically correct**, it is commonly stated this way for
ease of explanation. The kernel **does not actually schedule processes**, it
only schedules threads in the context of a process. For more on the
distinction between processes and threads, see the section Process Manager,
later in this chapter.
It is this procedure that makes preemptive multitasking ?possible?. Because it
is the kernel that schedules the execution of all code on the system, it [the
kernel] **cannot be preempted**. It also cannot be paged to disk for any
reason.
------------------------------------------ end
So, WinNT did not truly implement preemption... and the WinNT kernel was never
preemptable.
For information on when the linux kernel received its preemptive code patch
follow this link: http://www.linuxdevices.com/articles/AT4185744181.html
--
Kind regards,
M Harris <><
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