linux-kernel - [PATCH v5 net-next 11/11] skbuff: queue NAPI_MERGED_FREE skbs into NAPI cache instead of freeing

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Date:   Thu, 11 Feb 2021 18:55:24 +0000
From:   Alexander Lobakin <alobakin@...me>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Jonathan Lemon <jonathan.lemon@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Alexander Lobakin <alobakin@...me>,
        Randy Dunlap <rdunlap@...radead.org>,
        Kevin Hao <haokexin@...il.com>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Marco Elver <elver@...gle.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Alexander Duyck <alexanderduyck@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Taehee Yoo <ap420073@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Björn Töpel <bjorn@...nel.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Guillaume Nault <gnault@...hat.com>,
        Yonghong Song <yhs@...com>, zhudi <zhudi21@...wei.com>,
        Michal Kubecek <mkubecek@...e.cz>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Yang Yingliang <yangyingliang@...wei.com>,
        Florian Westphal <fw@...len.de>,
        Edward Cree <ecree.xilinx@...il.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH v5 net-next 11/11] skbuff: queue NAPI_MERGED_FREE skbs into NAPI cache instead of freeing

napi_frags_finish() and napi_skb_finish() can only be called inside
NAPI Rx context, so we can feed NAPI cache with skbuff_heads that
got NAPI_MERGED_FREE verdict instead of immediate freeing.
Replace __kfree_skb() with __kfree_skb_defer() in napi_skb_finish()
and move napi_skb_free_stolen_head() to skbuff.c, so it can drop skbs
to NAPI cache.
As many drivers call napi_alloc_skb()/napi_get_frags() on their
receive path, this becomes especially useful.

Signed-off-by: Alexander Lobakin <alobakin@...me>
---
 include/linux/skbuff.h |  1 +
 net/core/dev.c         |  9 +--------
 net/core/skbuff.c      | 12 +++++++++---
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 906122eac82a..6d0a33d1c0db 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2921,6 +2921,7 @@ static inline struct sk_buff *napi_alloc_skb(struct napi_struct *napi,
 }
 void napi_consume_skb(struct sk_buff *skb, int budget);
 
+void napi_skb_free_stolen_head(struct sk_buff *skb);
 void __kfree_skb_defer(struct sk_buff *skb);
 
 /**
diff --git a/net/core/dev.c b/net/core/dev.c
index 4154d4683bb9..6d2c7ae90a23 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6095,13 +6095,6 @@ struct packet_offload *gro_find_complete_by_type(__be16 type)
 }
 EXPORT_SYMBOL(gro_find_complete_by_type);
 
-static void napi_skb_free_stolen_head(struct sk_buff *skb)
-{
-	skb_dst_drop(skb);
-	skb_ext_put(skb);
-	kmem_cache_free(skbuff_head_cache, skb);
-}
-
 static gro_result_t napi_skb_finish(struct napi_struct *napi,
 				    struct sk_buff *skb,
 				    gro_result_t ret)
@@ -6115,7 +6108,7 @@ static gro_result_t napi_skb_finish(struct napi_struct *napi,
 		if (NAPI_GRO_CB(skb)->free == NAPI_GRO_FREE_STOLEN_HEAD)
 			napi_skb_free_stolen_head(skb);
 		else
-			__kfree_skb(skb);
+			__kfree_skb_defer(skb);
 		break;
 
 	case GRO_HELD:
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c8f3ea1d9fbb..85f0768a1144 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -917,9 +917,6 @@ static void napi_skb_cache_put(struct sk_buff *skb)
 	struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
 	u32 i;
 
-	/* drop skb->head and call any destructors for packet */
-	skb_release_all(skb);
-
 	kasan_poison_object_data(skbuff_head_cache, skb);
 	nc->skb_cache[nc->skb_count++] = skb;
 
@@ -936,6 +933,14 @@ static void napi_skb_cache_put(struct sk_buff *skb)
 
 void __kfree_skb_defer(struct sk_buff *skb)
 {
+	skb_release_all(skb);
+	napi_skb_cache_put(skb);
+}
+
+void napi_skb_free_stolen_head(struct sk_buff *skb)
+{
+	skb_dst_drop(skb);
+	skb_ext_put(skb);
 	napi_skb_cache_put(skb);
 }
 
@@ -961,6 +966,7 @@ void napi_consume_skb(struct sk_buff *skb, int budget)
 		return;
 	}
 
+	skb_release_all(skb);
 	napi_skb_cache_put(skb);
 }
 EXPORT_SYMBOL(napi_consume_skb);
-- 
2.30.1