Re: [PATCH] clean up FIXME in do_timer_interrupt

[George Anzinger]

Lee Revell wrote:
> On Fri, 2005-03-04 at 12:58 -0800, George Anzinger wrote:
>
> > Lee Revell wrote:
> >
> > > On Fri, 2005-03-04 at 02:28 -0800, George Anzinger wrote:
> > > The thing that brought this code to my attention is that with PREEMPT_RT
> > > this happens to be the longest non-preemptible code path in the kernel.
> > > On my 1.3 Ghz machine set_rtc_mmss takes about 50 usecs, combined with
> > > the rest of timer irq we end up disabling preemption for about 90 usecs.
> > > Unfortunately I don't have the trace anymore.
> > >
> > > Anyway the upshot is if we hung this off a timer it looks like we would
> > > improve the worst case latency with PREEMPT_RT by almost 50%.  Unless
> > > there is some reason it has to be done synchronously of course.
> >
> > Well, it does have to be done at the right WRT the second, but I suspect we can 
> > hit that as well with a timer as it is hit now.  Also, if we are _really_ off 
> > the mark, this can be defered till the next second.
>
>
> Do you have a patch?

Not at the moment, but I will work one up.
> Andrew merged my trivial patch to clean up the logic, but a real fix
> would be better.
>
> Lee

--
George Anzinger   george@xxxxxxxxxx
High-res-timers:  http://sourceforge.net/projects/high-res-timers/

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