mercredi 12 Avril 2006 08:25, you wrote/vous avez écrit :
>
> * Steven Rostedt <[email protected]> wrote:
>
> > > Why do we need such a size ?
> >
> > It seems that the -rt kernel has increased the size of structures that
> > are used in modules and are defined per cpu.
>
> i'm still wondering what that could be. The most drastic increase is the
> size of locks (spinlocks, mutexes, etc.), especially with debugging
> enabled - maybe one of the drivers uses a big per-CPU array of locks?
>
> ah. One thing that takes up _alot_ of per-CPU space is the
> latency-histogram stuff. I made the latency tracer itself use
> non-per-cpu constructs to avoid overflowing the per-cpu-area, but the
> latency-histogram code still uses PER_CPU:
>
...
>
> where MAX_ENTRY_NUM is 10240 right now. So the space used up is
> 10240*3*8 - roughly +256K per-cpu space!
I use effectively CONFIG_WAKEUP_LATENCY_HIST.
>
> I think that explains it. So the rule for -rt is, +256K more per-cpu
> area is needed if the latency histograms are turned on.
OK.
>
> Ingo
--
Serge Noiraud
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