netdev - [RFC PATCH net-next 4/4] net/core: handle GRO_NORMAL skbs as a list in napi_gro_receive

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Message-ID: <4c2ae895-c7d5-48fb-a045-ad23f091b4cc@solarflare.com>
Date:   Thu, 30 Aug 2018 21:01:06 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     <linux-net-drivers@...arflare.com>, <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>
Subject: [RFC PATCH net-next 4/4] net/core: handle GRO_NORMAL skbs as a list
 in napi_gro_receive_list

Allows GRO-using drivers to get the benefits of batching for non-GROable
 traffic.

Signed-off-by: Edward Cree <ecree@...arflare.com>
---
 net/core/dev.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index ac9741273c62..f9391f76feb7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5615,6 +5615,7 @@ EXPORT_SYMBOL(napi_gro_receive);
 int napi_gro_receive_list(struct napi_struct *napi, struct list_head *head)
 {
 	struct sk_buff *skb, *next;
+	struct list_head sublist;
 	gro_result_t result;
 	int kept = 0;
 
@@ -5624,14 +5625,26 @@ int napi_gro_receive_list(struct napi_struct *napi, struct list_head *head)
 		skb_gro_reset_offset(skb);
 	}
 
+	INIT_LIST_HEAD(&sublist);
 	list_for_each_entry_safe(skb, next, head, list) {
 		list_del(&skb->list);
 		skb->next = NULL;
 		result = dev_gro_receive(napi, skb);
-		result = napi_skb_finish(result, skb);
-		if (result != GRO_DROP)
-			kept++;
+		if (result == GRO_NORMAL) {
+			list_add_tail(&skb->list, &sublist);
+			continue;
+		} else {
+			if (!list_empty(&sublist)) {
+				/* Handle the GRO_NORMAL skbs to prevent OoO */
+				kept += netif_receive_skb_list_internal(&sublist);
+				INIT_LIST_HEAD(&sublist);
+			}
+			result = napi_skb_finish(result, skb);
+			if (result != GRO_DROP)
+				kept++;
+		}
 	}
+	kept += netif_receive_skb_list_internal(&sublist);
 	return kept;
 }
 EXPORT_SYMBOL(napi_gro_receive_list);