Hi,

Is the cost , in terms of CPU , when there occurs a context switch
between two kernel threads is the same as when
there is a context switch between two user space threads ?
Is this cost the same when there is a context switch between a kernel
thread and a user space thread ?

If you look at the implementation of kernel_thread() method (in i386 it's in
arch/i386/kernel/process.c), you will see that it ultimately
calls do_fork() ; in fact also when you create a user space process/thread by
fork() or pthread_create() you also ultimately call do_fork().

There are of course some differences between kernel threads
and user space threads.
for example : a kernel thread does not have any need for access to memory
of user space.

But do these differences cause a conetxt switch between 2 kernel
threads to be quicker ?

Rafi G.

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