Messages in this thread | | | Date | Tue, 5 May 2015 12:53:46 +0200 | From | Peter Zijlstra <> | Subject | Re: question about RCU dynticks_nesting |
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On Mon, May 04, 2015 at 12:39:23PM -0700, Paul E. McKenney wrote: > But in non-preemptible RCU, we have PREEMPT=n, so there is no preempt > counter in production kernels. Even if there was, we have to sample this > on other CPUs, so the overhead of preempt_disable() and preempt_enable() > would be where kernel entry/exit is, so I expect that this would be a > net loss in overall performance.
We unconditionally have the preempt_count, its just not used much for PREEMPT_COUNT=n kernels.
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