Re: [PATCH tip/core/rcu 01/22] rcu: Control RCU_FANOUT_LEAF from boot-time parameter

Josh Triplett
2012-07-01T07:18:13Z

On Sun, Jul 01, 2012 at 03:49:42PM +0930, Rusty Russell wrote:
> On Fri, 22 Jun 2012 08:17:00 -0700, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
> > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> >
> > Although making RCU_FANOUT_LEAF a kernel configuration parameter rather
> > than a fixed constant makes it easier for people to decrease cache-miss
> > overhead for large systems, it is of little help for people who must
> > run a single pre-built kernel binary.
> >
> > This commit therefore allows the value of RCU_FANOUT_LEAF to be
> > increased (but not decreased!) via a boot-time parameter named
> > rcutree.rcu_fanout_leaf.
> ...
> > +static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF;
> > +module_param(rcu_fanout_leaf, int, 0);
>
> Maybe it's overkill, but 0400 or 0444 might be a nice touch.

I agree. 0 almost never makes sense; root should almost always have the
ability to read module parameters. And in this case, I see no reason
not to make it 0444.

- Josh Triplett