Messages in this thread | | | From | "Serge Noiraud" <> | Subject | Re: PREEMPT_RT : 2.6.16-rt12 and boot : BUG ? | Date | Wed, 12 Apr 2006 09:23:05 +0200 |
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mercredi 12 Avril 2006 08:25, you wrote/vous avez écrit : > > * Steven Rostedt <rostedt@goodmis.org> 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
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