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

[Peter Zijlstra]

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.

> > 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.
--
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/