Re: [PATCH tip/core/rcu 0/2] v2 Add callback-free CPUs
On Wed, Oct 31, 2012 at 08:25:21AM +0100, Peter Zijlstra wrote:
> On Tue, 2012-10-30 at 20:45 -0700, Paul E. McKenney wrote:
> > This commit therefore adds the ability
> > for selected CPUs ("rcu_nocbs=" boot parameter) to have their
> > callbacks
> > offloaded to kthreads, inspired by Joe Korty's and Jim Houston's JRCU.
> > If the "rcu_nocb_poll" boot parameter is also specified, these
> > kthreads
> > will do polling, removing the need for the offloaded CPUs to do
> > wakeups.
>
> How much pain to make that dynamically configurable?
A fair amount of pain, though I do hope to make it runtime configurable
at some point. Known problems include races between changes in the
nocb configuration, rcu_barrier(), grace-period initialization, and
CPU hotplug. Should be solvable, but want to get the other bugs out of
the way first.
Thanx, Paul
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Re: [PATCH tip/core/rcu 0/2] v2 Add callback-free CPUs
On Tue, 2012-10-30 at 20:45 -0700, Paul E. McKenney wrote:
> This commit therefore adds the ability
> for selected CPUs ("rcu_nocbs=" boot parameter) to have their
> callbacks
> offloaded to kthreads, inspired by Joe Korty's and Jim Houston's JRCU.
> If the "rcu_nocb_poll" boot parameter is also specified, these
> kthreads
> will do polling, removing the need for the offloaded CPUs to do
> wakeups.
How much pain to make that dynamically configurable?
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip/core/rcu 0/2] v2 Add callback-free CPUs
On Tue, 2012-10-30 at 20:45 -0700, Paul E. McKenney wrote: This commit therefore adds the ability for selected CPUs (rcu_nocbs= boot parameter) to have their callbacks offloaded to kthreads, inspired by Joe Korty's and Jim Houston's JRCU. If the rcu_nocb_poll boot parameter is also specified, these kthreads will do polling, removing the need for the offloaded CPUs to do wakeups. How much pain to make that dynamically configurable? -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip/core/rcu 0/2] v2 Add callback-free CPUs
On Wed, Oct 31, 2012 at 08:25:21AM +0100, Peter Zijlstra wrote: On Tue, 2012-10-30 at 20:45 -0700, Paul E. McKenney wrote: This commit therefore adds the ability for selected CPUs (rcu_nocbs= boot parameter) to have their callbacks offloaded to kthreads, inspired by Joe Korty's and Jim Houston's JRCU. If the rcu_nocb_poll boot parameter is also specified, these kthreads will do polling, removing the need for the offloaded CPUs to do wakeups. How much pain to make that dynamically configurable? A fair amount of pain, though I do hope to make it runtime configurable at some point. Known problems include races between changes in the nocb configuration, rcu_barrier(), grace-period initialization, and CPU hotplug. Should be solvable, but want to get the other bugs out of the way first. Thanx, Paul -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
