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

Mark Hounschell
2008-08-26T17:59:39Z

Thomas Gleixner wrote:
> On Tue, 26 Aug 2008, Nick Piggin wrote:
>
>> On Tuesday 26 August 2008 19:30, Ingo Molnar wrote:
>>> * Nick Piggin <nickpiggin@yahoo.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