Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4]

K.R. Foley
2004-11-01T17:29:56Z

Ingo Molnar wrote:
> * Ingo Molnar <mingo@elte.hu> wrote:
>
>
>>>removing the poll() lines doesnt seem to impact the quality of the
>>>data, but i still see roughly 50 usecs added to the 'real' latency
>>>that i see in traces.
>>
>>this i think is related to what Thomas observed, that there's a new
>>irqs-off critical section somewhere. (it's in the new priority
>>handling code i think.)
>
>
> ah, found it. Only RT tasks were supposed to get special priority
> handling, while in fact all tasks got it - so when Thomas ran hackbench
> (Thomas, you did, right?) it created an O(nr_hackbench) overhead within
> the mutex code ... I've uploaded -V0.6.5 to the usual place:
>
> http://redhat.com/~mingo/realtime-preempt/
>

V0.6.5 built and booted fine on my SMP workstation. However, just a few
minutes after booting it exhibited behavior like a system does when you
can't fork any new processses.
The system was responsive.
I could switch between windows.
I could switch from X to a virtual terminal.
I could type in commands but they never return.
At the virtual terminal login I could type the login but never get a
passwd prompt.
Nothing in the logs during this timeframe.
Reset button was the only way to recover.

kr