On Sat, Jan 05, 2013 at 09:48:54AM -0800, Paul E. McKenney wrote: > From: "Paul E. McKenney" <paul.mcken...@linaro.org> > > Currently, the only way to specify no-CBs CPUs is via the rcu_nocbs > kernel command-line parameter. This is inconvenient in some cases, > particularly for randconfig testing, so this commit adds a new > RCU_NOCB_CPU_DEFAULT kernel configuration parameter. Setting this > new parameter to zero (the default) retains the old behavior, setting > it to one offloads callback processing from CPU 0 (along with any > other CPUs specified by the rcu_nocbs boot-time parameter), and setting > it to two offloads callback processing from all CPUs. > > Signed-off-by: Paul E. McKenney <paul.mcken...@linaro.org> > Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Comments below. > init/Kconfig | 13 +++++++++++++ > kernel/rcutree_plugin.h | 13 +++++++++++++ > 2 files changed, 26 insertions(+), 0 deletions(-) > > diff --git a/init/Kconfig b/init/Kconfig > index fc6a3ca..35dcedb 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -676,6 +676,19 @@ config RCU_NOCB_CPU > Say Y here if you want to help to debug reduced OS jitter. > Say N here if you are unsure. > > +config RCU_NOCB_CPU_DEFAULT > + int "Offload RCU callback processing from compile-selected CPUs" > + depends on RCU_NOCB_CPU > + range 0 2 > + default 0 > + help > + Set this option to zero to only offload RCU callback processing > + from those CPUs specified by the boot-time rcu_nocbs kernel > + parameter. Set it to one to offload processing from CPU 0 > + in addition to any CPUs specified at boot time. Set it to > + two to offload processing from all CPUs, regardless of the > + setting of the boot-time rcu_nocbs kernel parameter. > + Rather than making users translate the meanings of 0, 1, and 2, this seems like something better done with a choice/endchoice; that would then offer a menu of options that can each have their own description. Take a look at the "Memory split" option in arch/x86/Kconfig for an example. > --- a/kernel/rcutree_plugin.h > +++ b/kernel/rcutree_plugin.h > @@ -86,6 +86,19 @@ static void __init rcu_bootup_announce_oddness(void) > if (nr_cpu_ids != NR_CPUS) > printk(KERN_INFO "\tRCU restricting CPUs from NR_CPUS=%d to > nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids); > #ifdef CONFIG_RCU_NOCB_CPU > +#if CONFIG_RCU_NOCB_CPU_DEFAULT != 0 That would then make each of these conditionals self-documenting as well. - Josh Triplett -- 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/
