Re: [PATCH RFC] rcu: Permit limiting of force_quiescent_state()latency

[Mike Galbraith]

On Sun, 2012-03-18 at 17:10 -0700, Paul E. McKenney wrote:

> Thank you very much for your efforts on this!!!

No problem, irq holdoff troubles are worth effort.

> Given that you were seeing about 200-microsecond latency spikes on
> grace-period initialization, I would expect that you would need about
> 200 dyntick-idle CPUs for force_quiescent_state() to give you a
> ten-microsecond spike, so I am not surprised that you could not see
> the difference on 60 CPUs, which probably have given you something
> like 3 microseconds..

Crawling over fewer locks should still save cycles, so I'll measure.
Big box rt needs every little usec we can scrape together.

-Mike

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