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

[Arjan van de Ven]

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@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/