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I am referencing the Book Fundamentals of Computer Algorithms" by Ellis Horowitz et al.

At the part which they talk about multi-threading models, user-level and kernel-level thread are introduced.

And at the scheduling chapter, under multi-core processors, they talk about software threads and hardware threads.

Even though both sections are titled 'multithreading', one deals with how user-threads are mapped to kernel threads and the other deals with hyperthreading. (correct me if I am wrong)

I just want to know whether they are talking about the same terms. If not, will you clarify what is the difference between User-level threads vs software threads?

Thank you.

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Kernel threads and user threads are both software threads. This is only terminology, but I think that hardware threads in your book are the actual CPU cores including hyperthreading threads that the CPU can run at once. So a hardware thread is not instructions or an actual thread, it is simply the threads that the CPU supports. For example, if the CPU has 4 cores and each core uses hyperthreading to have 2 virtual threads each, then you would have 8 hardware threads available for software threads to run.

Kernel threads and user threads are separated by a permission bit in the page tables. Having a thread with a permission of 0 (kernel thread) doesn't make the thread a hardware thread. It is simply a software thread running in kernel mode.

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  • $\begingroup$ Yea, I think your answer is correct. If you are sure about the answer then I will mark it as answered. $\endgroup$
    – Midhunraj R Pillai
    Commented Jan 20, 2021 at 15:46

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