Question

can user level threads be scheduled on different processors in a multi-processor system.??

Comments

No arjun. If there are any previous year questions related to this please do share the links.

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wow great. that much pain u can take urself.

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:-).

Answer 1

No, they cannot be. In fact they cannot be executed as multiple threads (SMT) on a single core also as for the kernel, it has no idea of user threads.

Comments

And please elaborate on the difference between User thread and kernel thread. User threads make use of system calls to execute priviledge instructions. Will that spawn a new kernel thread?

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Arjun Sir, please explain why user-level threads can only be executed on a single processor only?

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Hello Sir

It's known that multithreading (user level thread) on multiprocessor is not beneficial as OS is unaware of the existence of user level threads but i'm doubtful about your comment like 'User level threads can't be even executed on uni-processor system' ?

Can you elaborate your argument because as per my knowledge i don't find any problem about multiple user level threads execution. We can achieve scheduling between user level threads through user level libraries.

I didn't do any research but i read it that some OS assign user level threads to kernel level processes for the purpose of scheduling.

Tell me if i went wrong somewhere.

Answer 2

Multiple user-level threads can run on different cores at the same time, IF they're running inside different kernel-level threads. If you only have ULT as a tool, you're limited to a single processor. If KLT are available, you can spread the kernel threads over multiple processors and dispatch your ULT among the available kernel threads

Comments

yes...that we can say it's many to many mapping of multithreaded process

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Explains everything.