Re: [PATCH] kthread: always create the kernel threads with normal priority

Hello Michal,

Maybe we can find a way to use a similar mechanism as I used in my
patchset for the priorities of the remaining kthreads.
I do not like the way of forcing userland to change the priorities,
because that would require a userland with the chrt tool installed,
and that is not that practical for embedded systems (in which there
could be cases that there is no userland at all, or the init-process
is the whole embedded application). In that case an option to do it on
the kernel commandline is more practical.

I propose this kernel cmd-line option:
kthread_pmap=somethread:50,otherthread:12,34

I see. kthreadd would look up the priority for itself and
kthread_create would consult the map for all other kernel threads.
That should work.
Your sirq_pmap would not be needed anymore, as kthread_pmap could be
used for softirq threads too, right?

That is correct. The soft-irqs are just ordinary kernel-threads, but
irq_pmap is still needed, to set the priority of a certain interrupt
handler.
In this case it also possible to set the prio of the IRQ-kthreads as
well as the prio of a certain interrupt handler. This might give some
conflicts, and I have to check how to resolve these.

Kind Regards,

Remy


2008/1/7, Michal Schmidt <mschmidt@xxxxxxxxxx>:
On Mon, 7 Jan 2008 12:22:51 +0100
"Remy Bohmer" <linux@xxxxxxxxxx> wrote:

Hello Michal and Andrew,

Let's not make the decision for the user. Just allow the
administrator to change kthreadd's priority safely if he chooses to
do it. Ensure that the kernel threads are created with the usual
nice level even if kthreadd's priority is changed from the default.

Last year, I posted a patchset (that was meant for Preempt-RT at that
time) to be able to prioritise the interrupt-handler-threads (which
are kthreads) and softirq-threads from the kernel commandline. See
http://lkml.org/lkml/2007/12/19/208

Maybe we can find a way to use a similar mechanism as I used in my
patchset for the priorities of the remaining kthreads.
I do not like the way of forcing userland to change the priorities,
because that would require a userland with the chrt tool installed,
and that is not that practical for embedded systems (in which there
could be cases that there is no userland at all, or the init-process
is the whole embedded application). In that case an option to do it on
the kernel commandline is more practical.

I propose this kernel cmd-line option:
kthread_pmap=somethread:50,otherthread:12,34

I see. kthreadd would look up the priority for itself and
kthread_create would consult the map for all other kernel threads.
That should work.
Your sirq_pmap would not be needed anymore, as kthread_pmap could be
used for softirq threads too, right?

Michal

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