Re: [PATCH tip/core/rcu 0/4] Programmatic nestable expedited grace periods

[Arjan van de Ven]

> > > > 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?

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