linux-kernel - Re: [PATCH]sched: fix typo in sched-rt-group.txt file

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Message-ID: <49b7c2350905120405w3591a92bj265dff000929a928@mail.gmail.com>
Date:	Tue, 12 May 2009 20:05:06 +0900
From:	GeunSik Lim <leemgs1@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	tglx <tglx@...utronix.de>, williams <williams@...hat.com>
Subject: Re: [PATCH]sched: fix typo in sched-rt-group.txt file

2009/5/12 Ingo Molnar <mingo@...e.hu>:
>
> * Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
>
>> On Tue, 2009-05-12 at 17:37 +0900, GeunSik Lim wrote:
>> >
>> >
>> > Dear Ingo,
>> >
>> > I found typo about the range of static priority ( = realtime priority )
>> > in "./Documentation/scheduler/sched-rt-group.txt" file.
>> >
>> > If I don't understand static priority levels, Correct me.
>>
>> Right, that 'confusion' stems from the fact that our in-kernel priority
>> lists do consider all 140 priorities.
>>
>> The patch looks good though.
>>
>> > commit d6af702008117ca489a2f5476239d1688a517e98
>> > Author: GeunSik,Lim <leemgs1@...il.com>
>> > Date:   Tue May 12 17:20:32 2009 +0900
>> >
>> >     sched: fix typo in sched-rt-group.txt file
>> >
>> >     Fix typo about static priority's range.
>> >      Kernel Space priority: 0   to 99   --> User Space RT priority 99 to 0
>> >      Kernel Space priority: 100 to 139  --> User Space nice -20 to 19
>> >
>> >     Signed-off-by: GeunSik Lim <geunsik.lim@...sung.com>
>> >
>> > diff --git a/Documentation/scheduler/sched-rt-group.txt b/Documentation/scheduler/sched-rt-group.txt
>> > index 5ba4d3f..1537146 100644
>> > --- a/Documentation/scheduler/sched-rt-group.txt
>> > +++ b/Documentation/scheduler/sched-rt-group.txt
>> > @@ -169,7 +169,7 @@ get their allocated time.
>> >
>> >  Implementing SCHED_EDF might take a while to complete. Priority Inheritance is
>> >  the biggest challenge as the current linux PI infrastructure is geared towards
>> > -the limited static priority levels 0-139. With deadline scheduling you need to
>> > +the limited static priority levels 0-99. With deadline scheduling you need to
>
> SCHED_FIFO goes from 1 to 99. So it's either 0-98 or 1-99. From
> sched_setscheduler(2):
>
>       Processes scheduled under one of  the  real-time  policies  (SCHED_FIFO,
>       SCHED_RR) have a sched_priority value in the range 1 (low) to 99 (high).
>
>        Ingo
>

Thank you for explanation about userspace rt priority's range like
sched_setscheduler(2).

Processes scheduled with SCHED_OTHER (or SCHED_BATCH) must be assigned
the static priority 0.  Processes scheduled under SCHED_FIFO (or
SCHED_RR) can have a static priority in the range 1 to 99.

So, I think that the below summary is right.
* Kernel Space priority: 0(high) to 99(low) --> User Space RT priority
99(high) to 0(low)

Is it incorrect?


-- 
Regards,
GeunSik Lim
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