From b58cc46c5f6b57f1c814e374dbc47176e6b4938e Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 2 Jul 2014 10:13:24 -0700 Subject: rcu: Don't offload callbacks unless specifically requested Enabling NO_HZ_FULL currently has the side effect of enabling callback offloading on all CPUs. This results in lots of additional rcuo kthreads, and can also increase context switching and wakeups, even in cases where callback offloading is neither needed nor particularly desirable. This commit therefore enables callback offloading on a given CPU only if specifically requested at build time or boot time, or if that CPU has been specifically designated (again, either at build time or boot time) as a nohz_full CPU. Signed-off-by: Paul E. McKenney --- init/Kconfig | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'init/Kconfig') diff --git a/init/Kconfig b/init/Kconfig index 9d76b99af1b9..9332d33346ac 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -737,7 +737,7 @@ choice config RCU_NOCB_CPU_NONE bool "No build_forced no-CBs CPUs" - depends on RCU_NOCB_CPU && !NO_HZ_FULL + depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL help This option does not force any of the CPUs to be no-CBs CPUs. Only CPUs designated by the rcu_nocbs= boot parameter will be @@ -751,7 +751,7 @@ config RCU_NOCB_CPU_NONE config RCU_NOCB_CPU_ZERO bool "CPU 0 is a build_forced no-CBs CPU" - depends on RCU_NOCB_CPU && !NO_HZ_FULL + depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL help This option forces CPU 0 to be a no-CBs CPU, so that its RCU callbacks are invoked by a per-CPU kthread whose name begins -- cgit v1.2.3-59-g8ed1b From ab74fdfd4e11ec040f21cf87edc14fc9f62cc934 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 4 May 2014 15:41:21 -0700 Subject: rcu: Handle obsolete references to TINY_PREEMPT_RCU Signed-off-by: Paul E. McKenney Reviewed-by: Lai Jiangshan --- include/linux/rcupdate.h | 17 ++++++++--------- init/Kconfig | 2 +- 2 files changed, 9 insertions(+), 10 deletions(-) (limited to 'init/Kconfig') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index c56ad15204ec..d231aa17b1d7 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -826,15 +826,14 @@ static inline void rcu_preempt_sleep_check(void) * read-side critical section that would block in a !PREEMPT kernel. * But if you want the full story, read on! * - * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), it - * is illegal to block while in an RCU read-side critical section. In - * preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU) - * in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may - * be preempted, but explicit blocking is illegal. Finally, in preemptible - * RCU implementations in real-time (with -rt patchset) kernel builds, - * RCU read-side critical sections may be preempted and they may also - * block, but only when acquiring spinlocks that are subject to priority - * inheritance. + * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), + * it is illegal to block while in an RCU read-side critical section. + * In preemptible RCU implementations (TREE_PREEMPT_RCU) in CONFIG_PREEMPT + * kernel builds, RCU read-side critical sections may be preempted, + * but explicit blocking is illegal. Finally, in preemptible RCU + * implementations in real-time (with -rt patchset) kernel builds, RCU + * read-side critical sections may be preempted and they may also block, but + * only when acquiring spinlocks that are subject to priority inheritance. */ static inline void rcu_read_lock(void) { diff --git a/init/Kconfig b/init/Kconfig index 9d76b99af1b9..977b37806e95 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -505,7 +505,7 @@ config PREEMPT_RCU def_bool TREE_PREEMPT_RCU help This option enables preemptible-RCU code that is common between - the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. + TREE_PREEMPT_RCU and, in the old days, TINY_PREEMPT_RCU. config RCU_STALL_COMMON def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE ) -- cgit v1.2.3-59-g8ed1b