From: Christoph Hellwig <[email protected]> Make smp_call_function_single and friends more efficient by using a lockless list.
Signed-off-by: Christoph Hellwig <[email protected]> Signed-off-by: Jan Kara <[email protected]> --- include/linux/elevator.h | 2 +- include/linux/smp.h | 7 ++++++- kernel/smp.c | 51 ++++++++++-------------------------------------- 3 files changed, 17 insertions(+), 43 deletions(-) diff --git a/include/linux/elevator.h b/include/linux/elevator.h index 306dd8cd0b6f..ec0e8f04c03c 100644 --- a/include/linux/elevator.h +++ b/include/linux/elevator.h @@ -211,7 +211,7 @@ enum { #define rq_entry_fifo(ptr) list_entry((ptr), struct request, queuelist) #define rq_fifo_clear(rq) do { \ list_del_init(&(rq)->queuelist); \ - INIT_LIST_HEAD(&(rq)->csd.list); \ + (rq)->csd.llist.next = NULL; \ } while (0) #else /* CONFIG_BLOCK */ diff --git a/include/linux/smp.h b/include/linux/smp.h index 5da22ee42e16..c0f38018c195 100644 --- a/include/linux/smp.h +++ b/include/linux/smp.h @@ -11,12 +11,17 @@ #include <linux/list.h> #include <linux/cpumask.h> #include <linux/init.h> +#include <linux/llist.h> extern void cpu_idle(void); typedef void (*smp_call_func_t)(void *info); struct call_single_data { - struct list_head list; + /* We still need list_head because of abuse by a block layer */ + union { + struct list_head list; + struct llist_node llist; + }; smp_call_func_t func; void *info; u16 flags; diff --git a/kernel/smp.c b/kernel/smp.c index bd9f94028838..47b415e16c24 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -28,12 +28,7 @@ struct call_function_data { static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); -struct call_single_queue { - struct list_head list; - raw_spinlock_t lock; -}; - -static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue); +static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue); static int hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) @@ -85,12 +80,8 @@ void __init call_function_init(void) void *cpu = (void *)(long)smp_processor_id(); int i; - for_each_possible_cpu(i) { - struct call_single_queue *q = &per_cpu(call_single_queue, i); - - raw_spin_lock_init(&q->lock); - INIT_LIST_HEAD(&q->list); - } + for_each_possible_cpu(i) + init_llist_head(&per_cpu(call_single_queue, i)); hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu); register_cpu_notifier(&hotplug_cfd_notifier); @@ -141,18 +132,9 @@ static void csd_unlock(struct call_single_data *csd) */ static void generic_exec_single(int cpu, struct call_single_data *csd, int wait) { - struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); - unsigned long flags; - int ipi; - if (wait) csd->flags |= CSD_FLAG_WAIT; - raw_spin_lock_irqsave(&dst->lock, flags); - ipi = list_empty(&dst->list); - list_add_tail(&csd->list, &dst->list); - raw_spin_unlock_irqrestore(&dst->lock, flags); - /* * The list addition should be visible before sending the IPI * handler locks the list to pull the entry off it because of @@ -164,7 +146,7 @@ static void generic_exec_single(int cpu, struct call_single_data *csd, int wait) * locking and barrier primitives. Generic code isn't really * equipped to do the right thing... */ - if (ipi) + if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu))) arch_send_call_function_single_ipi(cpu); if (wait) @@ -177,26 +159,19 @@ static void generic_exec_single(int cpu, struct call_single_data *csd, int wait) */ void generic_smp_call_function_single_interrupt(void) { - struct call_single_queue *q = &__get_cpu_var(call_single_queue); - LIST_HEAD(list); + struct llist_node *entry; + struct call_single_data *csd, *csd_next; /* * Shouldn't receive this interrupt on a cpu that is not yet online. */ WARN_ON_ONCE(!cpu_online(smp_processor_id())); - raw_spin_lock(&q->lock); - list_replace_init(&q->list, &list); - raw_spin_unlock(&q->lock); - - while (!list_empty(&list)) { - struct call_single_data *csd; - - csd = list_entry(list.next, struct call_single_data, list); - list_del(&csd->list); + entry = llist_del_all(&__get_cpu_var(call_single_queue)); + entry = llist_reverse_order(entry); + llist_for_each_entry_safe(csd, csd_next, entry, llist) { csd->func(csd->info); - csd_unlock(csd); } } @@ -411,17 +386,11 @@ void smp_call_function_many(const struct cpumask *mask, for_each_cpu(cpu, cfd->cpumask) { struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu); - struct call_single_queue *dst = - &per_cpu(call_single_queue, cpu); - unsigned long flags; csd_lock(csd); csd->func = func; csd->info = info; - - raw_spin_lock_irqsave(&dst->lock, flags); - list_add_tail(&csd->list, &dst->list); - raw_spin_unlock_irqrestore(&dst->lock, flags); + llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)); } /* Send a message to all CPUs in the map */ -- 1.8.1.4 -- 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/
