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Date: Fri, 20 Feb 2015 10:29:34 -0800 From: Arjan van de Ven <arjan@...ux.intel.com> To: paulmck@...ux.vnet.ibm.com CC: Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org, mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com, akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com, josh@...htriplett.org, tglx@...utronix.de, rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com, dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com Subject: Re: [PATCH tip/core/rcu 0/4] Programmatic nestable expedited grace periods On 2/20/2015 10:27 AM, Paul E. McKenney wrote: > On Fri, Feb 20, 2015 at 09:32:39AM -0800, Arjan van de Ven wrote: >>>>>> Does it really make a machine boot much faster? Why are people using >>>>>> synchronous gp primitives if they care about speed? Should we not fix >>>>>> that instead? >>>>> >>>>> The report I heard was that it provided 10-15% faster boot times. >>>> >>>> That's not insignificant; got more details? I think we should really >>>> look at why people are using the sync primitives. >>> >>> I must defer to the people who took the exact measurements. >>> >>> But yes, once I have that info, I should add it to the commit log. >> >> so the two most obvious cases are >> >> Registering sysrq keys ... even when the old key code had no handler >> (have a patch pending for this) >> >> registering idle handlers >> (this is more tricky, it's very obvious abuse but the fix is less clear) >> >> there's a few others as well that I'm chasing down... >> .. but the flip side, prior to running ring 3 code, why NOT do fast expedites? > > It would be good to have before-and-after measurements of actual > boot time. Are these numbers available? I'll make you pretty graphs when I get home from collab summit, which should be later today -- 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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