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Date: Mon, 19 Mar 2012 04:47:12 +0100 From: Mike Galbraith <efault@....de> To: paulmck@...ux.vnet.ibm.com Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com, akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com, josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu, dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com, fweisbec@...il.com, sivanich@....com Subject: Re: [PATCH RFC] rcu: Permit limiting of force_quiescent_state() latency 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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