Re: [PATCH tip/core/rcu 07/86] rcu: Force per-rcu_node kthreads off of the outgoing CPU

Paul E. McKenney
2011-05-02T10:25:27Z

On Sun, May 01, 2011 at 08:10:35AM -0700, Josh Triplett wrote:
> On Sun, May 01, 2011 at 06:20:47AM -0700, Paul E. McKenney wrote:
> > From: Paul E. McKenney <paul.mckenney@linaro.org>
> >
> > The scheduler has had some heartburn in the past when too many real-time
> > kthreads were affinitied to the outgoing CPU. So, this commit lightens
> > the load by forcing the per-rcu_node and the boost kthreads off of the
> > outgoing CPU. Note that RCU's per-CPU kthread remains on the outgoing
> > CPU until the bitter end, as it must in order to preserve correctness.
> >
> > Also avoid disabling hardirqs across calls to set_cpus_allowed_ptr(),
> > given that this function can block.
>
> This seems like two separate changes in one patch. The change to
> kernel/rcutree_plugin.h seems entirely separable from the change to
> kernel/rcutree.c here.
>
> > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>
> Heh, amusingly this actually seems meaningful, if you intend it as a
> "role" approval.

Yep, that is the intent! ;-)

Thanx, Paul