Re:Windows NT vs. Unix: A design comparison
by epcoa on Monday September 09, 2024 @05:13PM
(#41493961)
Processes and threads on NT are distinct nominative types of objects (in a system where “object” has a much more precise meaning) and the GP is at least correct that the former are not schedulable entities. This distinction doesn’t really exist on Linux for instance where there are at one approximation on the user side only processes (at least to use the verbiage of the clone syscall - look elsewhere and they’re threads in part due to having to support pthreads), and the scheduler schedules “tasks” (task_struct) (whereas in NT the “thread” nomenclature carries throughout). FreeBSD may have separate thread and proc internally but this is more an implementation detail. I guess this all to say at the level lower than an API like pthreads, process/thread really isn’t easily comparable between NT and most Unixes.
It’s not so much “heavyweight” vs “lightweight” but that NT has been by design more limited in how you can create new virtual memory spaces.
For better or worse NT tied the creation of VM spaces to this relatively expensive object to create which has made emulating Unix like behavior historically a pain in the ass.
Re:Windows NT vs. Unix: A design comparison
by PaulDavisThe1st on Monday September 09, 2024 @06:38PM
(#41494960)
pthreads is a user-space API, and has nothing to do with the kernel. It is possible to implement pthreads entirely in user space (though somewhat horrific to do so). Linux does not have kernel threads in order to support pthreads (though they help).
Anyway, I see your point about the bleed between the different semantics of a task_t in the linux kernel.
Re:Windows NT vs. Unix: A design comparison
by epcoa on Monday September 09, 2024 @07:33PM
(#41495464)
> Linux does not have kernel threads in order to support pthreads
Yes, what I was alluding to somewhat cryptically was things like tgids and the related tkill/tgkill syscalls that as far I am aware were added with the implementation of 1:1 pthread support in mind.
I am not sure what point you are attempting to make here. As written, it is more or less completely wrong.
NT and Unix kernels both execute threads. Threads can be created in a few microseconds. Processes are heavy weight on both NT and Unix kernels.
The only thing I can think of is the long-standing idea that Unix tends to encourage creating new processes and Windows-related OS kernels tend to encourage creating new threads. This is not false - process creation on Windows-related OS kernels is an extremely heavyweight process, certainly comparing it with any Unix. But it doesn't make the quote from you above correct.
On a separate note, the state of things at the point of creation of NT is really of very little interest other than than to computer historians. It has been more than 30 years, and every still-available Unix and presumably NT have continued to evolve since then. Linux has dozens to hundreds of design features in it that did not exist in any Unix when NT was released (and did not exist in NT either).