On Wed, Apr 17, 2013 at 06:24:48PM +0200, Frederic Weisbecker wrote: > We need full dynticks CPU to also be RCU nocb so > that we don't have to keep the tick to handle RCU > callbacks. > > Make sure the range passed to nohz_full= boot > parameter is a subset of rcu_nocbs= > > The CPUs that fail to meet this requirement will be > excluded from the nohz_full range. This is checked > early in boot time, before any CPU has the opportunity > to stop its tick. > > Suggested-by: Steven Rostedt <[email protected]> > Signed-off-by: Frederic Weisbecker <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: Chris Metcalf <[email protected]> > Cc: Christoph Lameter <[email protected]> > Cc: Geoff Levand <[email protected]> > Cc: Gilad Ben Yossef <[email protected]> > Cc: Hakan Akkan <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Kevin Hilman <[email protected]> > Cc: Li Zhong <[email protected]> > Cc: Paul E. McKenney <[email protected]> > Cc: Paul Gortmaker <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: Thomas Gleixner <[email protected]>
Reviewed-by: Paul E. McKenney <[email protected]> (And again, also updated documentation.) > --- > Documentation/kernel-parameters.txt | 2 ++ > include/linux/rcupdate.h | 7 +++++++ > include/linux/tick.h | 2 ++ > init/main.c | 1 + > kernel/rcutree.c | 6 +++--- > kernel/rcutree.h | 1 - > kernel/rcutree_plugin.h | 13 ++++--------- > kernel/time/tick-sched.c | 22 ++++++++++++++++------ > 8 files changed, 35 insertions(+), 19 deletions(-) > > diff --git a/Documentation/kernel-parameters.txt > b/Documentation/kernel-parameters.txt > index 887b297..4865e9b 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -1918,6 +1918,8 @@ bytes respectively. Such letter suffixes can also be > entirely omitted. > the specified list of CPUs whose tick will be stopped > whenever possible. The boot CPU will be forced outside > the range to maintain the timekeeping. > + The CPUs in this range must also be included in the > + rcu_nocbs= set. > > noiotrap [SH] Disables trapped I/O port accesses. > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > index b758ce1..8e0948c 100644 > --- a/include/linux/rcupdate.h > +++ b/include/linux/rcupdate.h > @@ -999,4 +999,11 @@ static inline notrace void > rcu_read_unlock_sched_notrace(void) > #define kfree_rcu(ptr, rcu_head) \ > __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) > > +#ifdef CONFIG_RCU_NOCB_CPU > +extern bool rcu_is_nocb_cpu(int cpu); > +#else > +static inline bool rcu_is_nocb_cpu(int cpu) { return false; } > +#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ > + > + > #endif /* __LINUX_RCUPDATE_H */ > diff --git a/include/linux/tick.h b/include/linux/tick.h > index b4e3b0c..0b6873c 100644 > --- a/include/linux/tick.h > +++ b/include/linux/tick.h > @@ -158,8 +158,10 @@ static inline u64 get_cpu_iowait_time_us(int cpu, u64 > *unused) { return -1; } > # endif /* !CONFIG_NO_HZ_COMMON */ > > #ifdef CONFIG_NO_HZ_FULL > +extern void tick_nohz_init(void); > extern int tick_nohz_full_cpu(int cpu); > #else > +static inline void tick_nohz_init(void) { } > static inline int tick_nohz_full_cpu(int cpu) { return 0; } > #endif > > diff --git a/init/main.c b/init/main.c > index 63534a1..2acb5bb 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -547,6 +547,7 @@ asmlinkage void __init start_kernel(void) > idr_init_cache(); > perf_event_init(); > rcu_init(); > + tick_nohz_init(); > radix_tree_init(); > /* init some links before init_ISA_irqs() */ > early_irq_init(); > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index f5ab502..1d4ceff 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -1695,7 +1695,7 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state > *rsp, > struct rcu_node *rnp, struct rcu_data *rdp) > { > /* No-CBs CPUs do not have orphanable callbacks. */ > - if (is_nocb_cpu(rdp->cpu)) > + if (rcu_is_nocb_cpu(rdp->cpu)) > return; > > /* > @@ -2757,10 +2757,10 @@ static void _rcu_barrier(struct rcu_state *rsp) > * corresponding CPU's preceding callbacks have been invoked. > */ > for_each_possible_cpu(cpu) { > - if (!cpu_online(cpu) && !is_nocb_cpu(cpu)) > + if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu)) > continue; > rdp = per_cpu_ptr(rsp->rda, cpu); > - if (is_nocb_cpu(cpu)) { > + if (rcu_is_nocb_cpu(cpu)) { > _rcu_barrier_trace(rsp, "OnlineNoCB", cpu, > rsp->n_barrier_done); > atomic_inc(&rsp->barrier_cpu_count); > diff --git a/kernel/rcutree.h b/kernel/rcutree.h > index f993c0a..38acc49 100644 > --- a/kernel/rcutree.h > +++ b/kernel/rcutree.h > @@ -529,7 +529,6 @@ static void print_cpu_stall_info(struct rcu_state *rsp, > int cpu); > static void print_cpu_stall_info_end(void); > static void zero_cpu_stall_ticks(struct rcu_data *rdp); > static void increment_cpu_stall_ticks(void); > -static bool is_nocb_cpu(int cpu); > static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, > bool lazy); > static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > index a5745e9..0cd91cc 100644 > --- a/kernel/rcutree_plugin.h > +++ b/kernel/rcutree_plugin.h > @@ -2167,7 +2167,7 @@ static int __init parse_rcu_nocb_poll(char *arg) > early_param("rcu_nocb_poll", parse_rcu_nocb_poll); > > /* Is the specified CPU a no-CPUs CPU? */ > -static bool is_nocb_cpu(int cpu) > +bool rcu_is_nocb_cpu(int cpu) > { > if (have_rcu_nocb_mask) > return cpumask_test_cpu(cpu, rcu_nocb_mask); > @@ -2225,7 +2225,7 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, > struct rcu_head *rhp, > bool lazy) > { > > - if (!is_nocb_cpu(rdp->cpu)) > + if (!rcu_is_nocb_cpu(rdp->cpu)) > return 0; > __call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy); > return 1; > @@ -2242,7 +2242,7 @@ static bool __maybe_unused > rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, > long qll = rsp->qlen_lazy; > > /* If this is not a no-CBs CPU, tell the caller to do it the old way. */ > - if (!is_nocb_cpu(smp_processor_id())) > + if (!rcu_is_nocb_cpu(smp_processor_id())) > return 0; > rsp->qlen = 0; > rsp->qlen_lazy = 0; > @@ -2282,7 +2282,7 @@ static bool nocb_cpu_expendable(int cpu) > * If there are no no-CB CPUs or if this CPU is not a no-CB CPU, > * then offlining this CPU is harmless. Let it happen. > */ > - if (!have_rcu_nocb_mask || is_nocb_cpu(cpu)) > + if (!have_rcu_nocb_mask || rcu_is_nocb_cpu(cpu)) > return 1; > > /* If no memory, play it safe and keep the CPU around. */ > @@ -2464,11 +2464,6 @@ static void __init rcu_init_nocb(void) > > #else /* #ifdef CONFIG_RCU_NOCB_CPU */ > > -static bool is_nocb_cpu(int cpu) > -{ > - return false; > -} > - > static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, > bool lazy) > { > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > index 2bac5ea..d71a5f2 100644 > --- a/kernel/time/tick-sched.c > +++ b/kernel/time/tick-sched.c > @@ -203,17 +203,27 @@ static int __cpuinit tick_nohz_cpu_down_callback(struct > notifier_block *nfb, > */ > static char __initdata nohz_full_buf[NR_CPUS + 1]; > > -static int __init init_tick_nohz_full(void) > +void __init tick_nohz_init(void) > { > - if (have_nohz_full_mask) > - cpu_notifier(tick_nohz_cpu_down_callback, 0); > + int cpu; > + > + if (!have_nohz_full_mask) > + return; > + > + cpu_notifier(tick_nohz_cpu_down_callback, 0); > + > + /* Make sure full dynticks CPU are also RCU nocbs */ > + for_each_cpu(cpu, nohz_full_mask) { > + if (!rcu_is_nocb_cpu(cpu)) { > + pr_warning("NO_HZ: CPU %d is not RCU nocb: " > + "cleared from nohz_full range", cpu); > + cpumask_clear_cpu(cpu, nohz_full_mask); > + } > + } > > cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), nohz_full_mask); > pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf); > - > - return 0; > } > -core_initcall(init_tick_nohz_full); > #else > #define have_nohz_full_mask (0) > #endif > -- > 1.7.5.4 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
