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Date: Fri, 24 Jul 2009 22:04:16 +0800
Message-ID: <454c71700907240704o32dcdeb3v57845eb9472dd04c@mail.gmail.com>
Subject: Re: report a bug about sched_rt
From: sen wang <wangsen.linux@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@elte.hu, akpm@linux-foundation.org, kernel@kolivas.org,
       npiggin@suse.de, arjan@infradead.org,
       linux-arm-kernel@lists.arm.linux.org.uk, linux-kernel@vger.kernel.org
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2009/7/24 Peter Zijlstra <peterz@infradead.org>:
> On Fri, 2009-07-24 at 21:44 +0800, sen wang wrote:
>> 2009/7/24 Peter Zijlstra <peterz@infradead.org>:
>> > On Fri, 2009-07-24 at 21:26 +0800, sen wang wrote:
>> >> don't tell me what theory. don't be so doctrinairism! OK?
>> >> If cpu is free and there is a running state task,how can you scdedule
>> >> idle task up?
>> >> I tell you again:we are not talking about a bandwidth of 100% for RT!
>> >> Bug lies in the bandwidth of (100- X)%.(X<100)
>> >> even in the time of 100-X,if there is a rt task, you should not idle()
>> >> the system.
>> >
>> > *sigh*
>> >
>> > Yes we should. I appreciate that you might assume otherwise, but you're
>> > wrong. Suppose you have two competing bandwidth groups, which one will
>> > run over, to what purpose?
>> >
>> > Also, your next top post will go to /dev/null.
>> >
>>
>>
>> OK !  maybe you has not understand what I said.
>> It not two competing bandwidth groups. there is a  active group and
>> another is empty?
>> How you do?
>
> No, but the 1 group is the trivial case of many groups. Changing the
> semantics for the trivial case is inconsistent at best, and confusing at
> worst.
>
>> Why not try it by your hand: empty the fair task, run a rt task,enable
>> the  bandwidth and
>> see what will happen!
>
> Oh, I know, I wrote the code.
>
>> In many embedded system,idle task will lead to shutdown something, but
>> the rt task will
>> assume: when it run, idle will not happen!
>
> How is it my problem when you design your system wrong?
>
> If you want your 1 RT group to not get throttled, disable the throttle,
> or adjust it to fit the parameters of your workload. If you don't want
> idle to have latency impact on your RT tasks, fix your idle behaviour.
>
>
>

OK
just one question:
if cpu is free and there is running state task, how you do?
schedule the task up? or schedule idle task up?
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