linux-kernel - Re: [PATCH 6/6] sched: disabled rt-bandwidth by default

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Date:	Tue, 26 Aug 2008 09:47:33 -0400
From:	Mark Hounschell <markh@...pro.net>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Nick Piggin <nickpiggin@...oo.com.au>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org,
	Stefani Seibold <stefani@...bold.net>,
	Dario Faggioli <raistlin@...ux.it>,
	Max Krasnyansky <maxk@...lcomm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 6/6] sched: disabled rt-bandwidth by default

Thomas Gleixner wrote:
> On Tue, 26 Aug 2008, Nick Piggin wrote:
> 
>> On Tuesday 26 August 2008 19:30, Ingo Molnar wrote:
>>> * Nick Piggin <nickpiggin@...oo.com.au> wrote:
>>>> So... no reply to this? I'm really wondering how it's OK to break
>>>> documented standards and previous Linux behaviour by default for
>>>> something that it is trivial to solve in userspace? [...]
>>> I disagree
>> Your arguments were along the line of:
>>
>> * It probably doesn't break anything (except we had somebody report
>>   that it breaks their app)
> 
> I'm a real-time oldtimer. An application which hogs the CPU for 9.9
> seconds with SCHED_FIFO priority is just broken. It's broken beyond
> all limits, whether POSIX allows to do that or Linux obeyed the
> request of the braindamaged application design.
> 

Well, I've been working on RT hardware (mostly) and software since 1977.
With all due respect, thats crapola. I for one have this requirement and
there is _no_ way around it in my world. In fact it's the kernel thats broke
by stealing precious usecs from me.

>From my point of view, as an RT user, any kernel that supports SMP yet can't 
guarantee me %100 of even one _my_ processors is just a plainly broken kernel. 

>> * If it does break something then they must be doing something stupid
>>   (I refuted that because there are several legitimate ways to use rt
>>   scheduling that is broken by this)
>>
>> * We have many other APIs and tools that don't conform to posix (why
>>   is that a reason to break this one?)
> 
> Simply because we use common sense instead of following every single
> POSIX brainfart by the letter.
> 
>> * We should break the API to cater for stupid users and distros who
>>   create local DoS and/or lock up their boxes (except this is trivial
>>   to solve by setting sysctls or having a watchdog or using sysrq)
> 
> For the vast majority of users and RT developers a sane default of
> sanity measures is useful and sensible. 
> 
> If someone wants to shoot himself in the foot then it's not an
> unreasonable request that he needs to disable the safety guards before
> pulling the trigger.
> 

Again that is also crapola. If i want to shoot myself in the foot, it's
none of your concern. I know perfectly well what will happen when 
I pull the trigger. 

My 2 cents
Regards
Mark
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