Messages in this thread | | | Date | Fri, 20 Feb 2015 09:14:42 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu 0/4] Programmatic nestable expedited grace periods |
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On Fri, Feb 20, 2015 at 05:54:09PM +0100, Peter Zijlstra wrote: > On Fri, Feb 20, 2015 at 08:37:37AM -0800, Paul E. McKenney wrote: > > On Fri, Feb 20, 2015 at 10:11:07AM +0100, Peter Zijlstra wrote: > > > So I though we wanted to get rid / limit the expedited stuff because its > > > IPI happy, and here its spreading. > > > > Well, at least it no longer IPIs idle CPUs. ;-) > > > > And this is during boot, when a few extra IPIs should not be a big deal. > > Well the one application now is during boot; but you expose the > interface for all to use, and therefore someone will.
I could make rcu_expedite_gp() and rcu_unexpedite_gp() be static, I suppose. Except that I need to test them with rcutorture. I suppose I could put the declaration in rcutorture.c, but then 0day will tell me to made them static. :-/
> > > 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.
Thanx, Paul
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