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Date:   Fri, 14 Jun 2019 06:00:25 -0700
From:   tip-bot for Waiman Long <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        hpa@...or.com, tglx@...utronix.de, cai@....us, longman@...hat.com,
        zhongjiang@...wei.com, joel@...lfernandes.org, mingo@...nel.org,
        yang.shi@...ux.alibaba.com
Subject: [tip:core/debugobjects] debugobjects: Reduce number of pool_lock
 acquisitions in fill_pool()

Commit-ID:  d26bf5056fc087d845bfbb8b651b4be2933ab7a6
Gitweb:     https://git.kernel.org/tip/d26bf5056fc087d845bfbb8b651b4be2933ab7a6
Author:     Waiman Long <longman@...hat.com>
AuthorDate: Mon, 20 May 2019 10:14:48 -0400
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 14 Jun 2019 14:51:15 +0200

debugobjects: Reduce number of pool_lock acquisitions in fill_pool()

In fill_pool(), the pool_lock is acquired and then released once per debug
object. If many objects are to be filled, the constant lock and unlock
operations are extra overhead.

To reduce the overhead, batch them up and do an allocation of 4 objects per
lock/unlock sequence.

Signed-off-by: Waiman Long <longman@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Yang Shi <yang.shi@...ux.alibaba.com>
Cc: "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc: Qian Cai <cai@....us>
Cc: Zhong Jiang <zhongjiang@...wei.com>
Link: https://lkml.kernel.org/r/20190520141450.7575-4-longman@redhat.com

---
 lib/debugobjects.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 714459a8dc10..7ea19fa63561 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -120,7 +120,7 @@ static const char *obj_states[ODEBUG_STATE_MAX] = {
 static void fill_pool(void)
 {
 	gfp_t gfp = GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN;
-	struct debug_obj *new, *obj;
+	struct debug_obj *obj;
 	unsigned long flags;
 
 	if (likely(obj_pool_free >= debug_objects_pool_min_level))
@@ -136,7 +136,7 @@ static void fill_pool(void)
 		 * Recheck with the lock held as the worker thread might have
 		 * won the race and freed the global free list already.
 		 */
-		if (obj_nr_tofree) {
+		while (obj_nr_tofree && (obj_pool_free < obj_pool_min_free)) {
 			obj = hlist_entry(obj_to_free.first, typeof(*obj), node);
 			hlist_del(&obj->node);
 			obj_nr_tofree--;
@@ -150,15 +150,23 @@ static void fill_pool(void)
 		return;
 
 	while (obj_pool_free < debug_objects_pool_min_level) {
+		struct debug_obj *new[ODEBUG_BATCH_SIZE];
+		int cnt;
 
-		new = kmem_cache_zalloc(obj_cache, gfp);
-		if (!new)
+		for (cnt = 0; cnt < ODEBUG_BATCH_SIZE; cnt++) {
+			new[cnt] = kmem_cache_zalloc(obj_cache, gfp);
+			if (!new[cnt])
+				break;
+		}
+		if (!cnt)
 			return;
 
 		raw_spin_lock_irqsave(&pool_lock, flags);
-		hlist_add_head(&new->node, &obj_pool);
-		debug_objects_allocated++;
-		obj_pool_free++;
+		while (cnt) {
+			hlist_add_head(&new[--cnt]->node, &obj_pool);
+			debug_objects_allocated++;
+			obj_pool_free++;
+		}
 		raw_spin_unlock_irqrestore(&pool_lock, flags);
 	}
 }
@@ -280,7 +288,7 @@ static void free_obj_work(struct work_struct *work)
 	/*
 	 * The objs on the pool list might be allocated before the work is
 	 * run, so recheck if pool list it full or not, if not fill pool
-	 * list from the global free list
+	 * list from the global free list.
 	 */
 	while (obj_nr_tofree && obj_pool_free < debug_objects_pool_size) {
 		obj = hlist_entry(obj_to_free.first, typeof(*obj), node);

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