From 634d61f45d6f668fe7e468b62d00ae469a583ca2 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Mon, 20 May 2019 10:14:47 -0400 Subject: [PATCH] debugobjects: Percpu pool lookahead freeing/allocation Most workloads will allocate a bunch of memory objects, work on them and then freeing all or most of them. So just having a percpu free pool may not reduce the pool_lock contention significantly if large number of objects are being used. To help those situations, we are now doing lookahead allocation and freeing of the debug objects into and out of the percpu free pool. This will hopefully reduce the number of times the pool_lock needs to be taken and hence its contention level. Signed-off-by: Waiman Long Signed-off-by: Thomas Gleixner Cc: Andrew Morton Cc: Yang Shi Cc: "Joel Fernandes (Google)" Cc: Qian Cai Cc: Zhong Jiang Link: https://lkml.kernel.org/r/20190520141450.7575-3-longman@redhat.com --- lib/debugobjects.c | 75 ++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 69 insertions(+), 6 deletions(-) diff --git a/lib/debugobjects.c b/lib/debugobjects.c index 38c23b528f6f..714459a8dc10 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -26,6 +26,7 @@ #define ODEBUG_POOL_SIZE 1024 #define ODEBUG_POOL_MIN_LEVEL 256 #define ODEBUG_POOL_PERCPU_SIZE 64 +#define ODEBUG_BATCH_SIZE 16 #define ODEBUG_CHUNK_SHIFT PAGE_SHIFT #define ODEBUG_CHUNK_SIZE (1 << ODEBUG_CHUNK_SHIFT) @@ -203,11 +204,10 @@ static struct debug_obj *__alloc_object(struct hlist_head *list) static struct debug_obj * alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr) { - struct debug_percpu_free *percpu_pool; + struct debug_percpu_free *percpu_pool = this_cpu_ptr(&percpu_obj_pool); struct debug_obj *obj; if (likely(obj_cache)) { - percpu_pool = this_cpu_ptr(&percpu_obj_pool); obj = __alloc_object(&percpu_pool->free_objs); if (obj) { percpu_pool->obj_free--; @@ -219,10 +219,32 @@ alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr) obj = __alloc_object(&obj_pool); if (obj) { obj_pool_used++; + obj_pool_free--; + + /* + * Looking ahead, allocate one batch of debug objects and + * put them into the percpu free pool. + */ + if (likely(obj_cache)) { + int i; + + for (i = 0; i < ODEBUG_BATCH_SIZE; i++) { + struct debug_obj *obj2; + + obj2 = __alloc_object(&obj_pool); + if (!obj2) + break; + hlist_add_head(&obj2->node, + &percpu_pool->free_objs); + percpu_pool->obj_free++; + obj_pool_used++; + obj_pool_free--; + } + } + if (obj_pool_used > obj_pool_max_used) obj_pool_max_used = obj_pool_used; - obj_pool_free--; if (obj_pool_free < obj_pool_min_free) obj_pool_min_free = obj_pool_free; } @@ -288,22 +310,39 @@ static void free_obj_work(struct work_struct *work) static bool __free_object(struct debug_obj *obj) { + struct debug_obj *objs[ODEBUG_BATCH_SIZE]; + struct debug_percpu_free *percpu_pool; + int lookahead_count = 0; unsigned long flags; bool work; - struct debug_percpu_free *percpu_pool; local_irq_save(flags); + if (!obj_cache) + goto free_to_obj_pool; + /* * Try to free it into the percpu pool first. */ percpu_pool = this_cpu_ptr(&percpu_obj_pool); - if (obj_cache && percpu_pool->obj_free < ODEBUG_POOL_PERCPU_SIZE) { + if (percpu_pool->obj_free < ODEBUG_POOL_PERCPU_SIZE) { hlist_add_head(&obj->node, &percpu_pool->free_objs); percpu_pool->obj_free++; local_irq_restore(flags); return false; } + /* + * As the percpu pool is full, look ahead and pull out a batch + * of objects from the percpu pool and free them as well. + */ + for (; lookahead_count < ODEBUG_BATCH_SIZE; lookahead_count++) { + objs[lookahead_count] = __alloc_object(&percpu_pool->free_objs); + if (!objs[lookahead_count]) + break; + percpu_pool->obj_free--; + } + +free_to_obj_pool: raw_spin_lock(&pool_lock); work = (obj_pool_free > debug_objects_pool_size) && obj_cache; obj_pool_used--; @@ -311,9 +350,25 @@ static bool __free_object(struct debug_obj *obj) if (work) { obj_nr_tofree++; hlist_add_head(&obj->node, &obj_to_free); + if (lookahead_count) { + obj_nr_tofree += lookahead_count; + obj_pool_used -= lookahead_count; + while (lookahead_count) { + hlist_add_head(&objs[--lookahead_count]->node, + &obj_to_free); + } + } } else { obj_pool_free++; hlist_add_head(&obj->node, &obj_pool); + if (lookahead_count) { + obj_pool_free += lookahead_count; + obj_pool_used -= lookahead_count; + while (lookahead_count) { + hlist_add_head(&objs[--lookahead_count]->node, + &obj_pool); + } + } } raw_spin_unlock(&pool_lock); local_irq_restore(flags); @@ -1228,7 +1283,7 @@ free: */ void __init debug_objects_mem_init(void) { - int cpu; + int cpu, extras; if (!debug_objects_enabled) return; @@ -1253,4 +1308,12 @@ void __init debug_objects_mem_init(void) pr_warn("out of memory.\n"); } else debug_objects_selftest(); + + /* + * Increase the thresholds for allocating and freeing objects + * according to the number of possible CPUs available in the system. + */ + extras = num_possible_cpus() * ODEBUG_BATCH_SIZE; + debug_objects_pool_size += extras; + debug_objects_pool_min_level += extras; }