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[v4,bpf-next,06/14] bpf: Further refactor alloc_bulk().

Message ID 20230706033447.54696-7-alexei.starovoitov@gmail.com (mailing list archive)
State Accepted
Commit 7468048237b8a99c03e1325b11373f9b29ef4139
Headers show
Series bpf: Introduce bpf_mem_cache_free_rcu(). | expand

Commit Message

Alexei Starovoitov July 6, 2023, 3:34 a.m. UTC 
From: Alexei Starovoitov <ast@kernel.org>

In certain scenarios alloc_bulk() might be taking free objects mainly from
free_by_rcu_ttrace list. In such case get_memcg() and set_active_memcg() are
redundant, but they show up in perf profile. Split the loop and only set memcg
when allocating from slab. No performance difference in this patch alone, but
it helps in combination with further patches.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Hou Tao <houtao1@huawei.com>
---
 kernel/bpf/memalloc.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)
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Patch

diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c
index 052fc801fb9f..0ee566a7719a 100644
--- a/kernel/bpf/memalloc.c
+++ b/kernel/bpf/memalloc.c
@@ -196,8 +196,6 @@  static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node)
 	void *obj;
 	int i;
 
-	memcg = get_memcg(c);
-	old_memcg = set_active_memcg(memcg);
 	for (i = 0; i < cnt; i++) {
 		/*
 		 * free_by_rcu_ttrace is only manipulated by irq work refill_work().
@@ -212,16 +210,24 @@  static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node)
 		 * numa node and it is not a guarantee.
 		 */
 		obj = __llist_del_first(&c->free_by_rcu_ttrace);
-		if (!obj) {
-			/* Allocate, but don't deplete atomic reserves that typical
-			 * GFP_ATOMIC would do. irq_work runs on this cpu and kmalloc
-			 * will allocate from the current numa node which is what we
-			 * want here.
-			 */
-			obj = __alloc(c, node, GFP_NOWAIT | __GFP_NOWARN | __GFP_ACCOUNT);
-			if (!obj)
-				break;
-		}
+		if (!obj)
+			break;
+		add_obj_to_free_list(c, obj);
+	}
+	if (i >= cnt)
+		return;
+
+	memcg = get_memcg(c);
+	old_memcg = set_active_memcg(memcg);
+	for (; i < cnt; i++) {
+		/* Allocate, but don't deplete atomic reserves that typical
+		 * GFP_ATOMIC would do. irq_work runs on this cpu and kmalloc
+		 * will allocate from the current numa node which is what we
+		 * want here.
+		 */
+		obj = __alloc(c, node, GFP_NOWAIT | __GFP_NOWARN | __GFP_ACCOUNT);
+		if (!obj)
+			break;
 		add_obj_to_free_list(c, obj);
 	}
 	set_active_memcg(old_memcg);