diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 8 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 66 |
2 files changed, 70 insertions, 4 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index fb95fad81c79..befaa63652ff 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4038,6 +4038,14 @@ latencies, which will choose a value aligned with the appropriate hardware boundaries. + rcutree.rcu_min_cached_objs= [KNL] + Minimum number of objects which are cached and + maintained per one CPU. Object size is equal + to PAGE_SIZE. The cache allows to reduce the + pressure to page allocator, also it makes the + whole algorithm to behave better in low memory + condition. + rcutree.jiffies_till_first_fqs= [KNL] Set delay from grace-period initialization to first attempt to force quiescent states. diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index a42a4693f161..37c0cd0332f8 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -175,6 +175,15 @@ module_param(gp_init_delay, int, 0444); static int gp_cleanup_delay; module_param(gp_cleanup_delay, int, 0444); +/* + * This rcu parameter is runtime-read-only. It reflects + * a minimum allowed number of objects which can be cached + * per-CPU. Object size is equal to one page. This value + * can be changed at boot time. + */ +static int rcu_min_cached_objs = 2; +module_param(rcu_min_cached_objs, int, 0444); + /* Retrieve RCU kthreads priority for rcutorture */ int rcu_get_gp_kthreads_prio(void) { @@ -2997,7 +3006,6 @@ struct kfree_rcu_cpu_work { * struct kfree_rcu_cpu - batch up kfree_rcu() requests for RCU grace period * @head: List of kfree_rcu() objects not yet waiting for a grace period * @bhead: Bulk-List of kfree_rcu() objects not yet waiting for a grace period - * @bcached: Keeps at most one object for later reuse when build chain blocks * @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period * @lock: Synchronize access to this structure * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES @@ -3013,13 +3021,22 @@ struct kfree_rcu_cpu_work { struct kfree_rcu_cpu { struct rcu_head *head; struct kfree_rcu_bulk_data *bhead; - struct kfree_rcu_bulk_data *bcached; struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES]; raw_spinlock_t lock; struct delayed_work monitor_work; bool monitor_todo; bool initialized; int count; + + /* + * A simple cache list that contains objects for + * reuse purpose. In order to save some per-cpu + * space the list is singular. Even though it is + * lockless an access has to be protected by the + * per-cpu lock. + */ + struct llist_head bkvcache; + int nr_bkv_objs; }; static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = { @@ -3056,6 +3073,31 @@ krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags) local_irq_restore(flags); } +static inline struct kfree_rcu_bulk_data * +get_cached_bnode(struct kfree_rcu_cpu *krcp) +{ + if (!krcp->nr_bkv_objs) + return NULL; + + krcp->nr_bkv_objs--; + return (struct kfree_rcu_bulk_data *) + llist_del_first(&krcp->bkvcache); +} + +static inline bool +put_cached_bnode(struct kfree_rcu_cpu *krcp, + struct kfree_rcu_bulk_data *bnode) +{ + // Check the limit. + if (krcp->nr_bkv_objs >= rcu_min_cached_objs) + return false; + + llist_add((struct llist_node *) bnode, &krcp->bkvcache); + krcp->nr_bkv_objs++; + return true; + +} + /* * This function is invoked in workqueue context after a grace period. * It frees all the objects queued on ->bhead_free or ->head_free. @@ -3091,7 +3133,12 @@ static void kfree_rcu_work(struct work_struct *work) kfree_bulk(bhead->nr_records, bhead->records); rcu_lock_release(&rcu_callback_map); - if (cmpxchg(&krcp->bcached, NULL, bhead)) + krcp = krc_this_cpu_lock(&flags); + if (put_cached_bnode(krcp, bhead)) + bhead = NULL; + krc_this_cpu_unlock(krcp, flags); + + if (bhead) free_page((unsigned long) bhead); cond_resched_tasks_rcu_qs(); @@ -3224,7 +3271,7 @@ kfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp, /* Check if a new block is required. */ if (!krcp->bhead || krcp->bhead->nr_records == KFREE_BULK_MAX_ENTR) { - bnode = xchg(&krcp->bcached, NULL); + bnode = get_cached_bnode(krcp); if (!bnode) { WARN_ON_ONCE(sizeof(struct kfree_rcu_bulk_data) > PAGE_SIZE); @@ -4277,12 +4324,23 @@ static void __init kfree_rcu_batch_init(void) for_each_possible_cpu(cpu) { struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); + struct kfree_rcu_bulk_data *bnode; for (i = 0; i < KFREE_N_BATCHES; i++) { INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work); krcp->krw_arr[i].krcp = krcp; } + for (i = 0; i < rcu_min_cached_objs; i++) { + bnode = (struct kfree_rcu_bulk_data *) + __get_free_page(GFP_NOWAIT | __GFP_NOWARN); + + if (bnode) + put_cached_bnode(krcp, bnode); + else + pr_err("Failed to preallocate for %d CPU!\n", cpu); + } + INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor); krcp->initialized = true; } |