Kernel threads and system usage metric.

[Chetan Nanda]

On Mar 9, 2012 11:57 PM, "Mulyadi Santosa" <mulyadi.santosa at gmail.com>
wrote:
>
> Hi :)
>
> On Fri, Mar 9, 2012 at 18:39, Daniel Hilst <danielhilst at gmail.com> wrote:
> > The processes that appear in top with brackets are the kernel threads?
>
> Yup :)
>
> > If so, this threads spend all its time on system mode, right?
>
> Yes, it supposed to ...
>
> >By the
> > system mode I mean the %sy on top header, since kernel threads hasn't
> > any memory mapped to user space, it can't run on user space at any time,
> > right?
>
> IIRC, kernel thread simply "borrow" any previous scheduled task's
> address space. In that matter, it also has user address space. So, if
> wanted, kernel thread could access user space. But normally it doesn't
> do it.
>
AFAIK kernel threads do not have any userspace context. As it is never
gaurnted which userspace process was previously running when kernel thread
scheduled to run.

> >
> >
> > So the total of system mode usage is the sum of all processes processing
> > in kernel space, plus the kernel threads processing, right?
>
> remember that kernel threads are also processes, so no need to
> differentiate between normal processes and kernel threads, especially
> when we talk about CPU utilization.
>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com
> training: mulyaditraining.blogspot.com
>
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