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Message-ID: <32107deb-d2be-19d7-c2c0-755af889c082@solarflare.com>
Date: Fri, 29 Jun 2018 20:31:10 +0100
From: Edward Cree <ecree@...arflare.com>
To: <davem@...emloft.net>
CC: <netdev@...r.kernel.org>
Subject: [PATCH v3 net-next 6/9] net: core: propagate SKB lists through
packet_type lookup
__netif_receive_skb_core() does a depressingly large amount of per-packet
work that can't easily be listified, because the another_round looping
makes it nontrivial to slice up into smaller functions.
Fortunately, most of that work disappears in the fast path:
* Hardware devices generally don't have an rx_handler
* Unless you're tcpdumping or something, there is usually only one ptype
* VLAN processing comes before the protocol ptype lookup, so doesn't force
a pt_prev deliver
so normally, __netif_receive_skb_core() will run straight through and pass
back the one ptype found in ptype_base[hash of skb->protocol].
Signed-off-by: Edward Cree <ecree@...arflare.com>
---
net/core/dev.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 64 insertions(+), 8 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index d2454678bc82..edd67b1f1e12 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4494,7 +4494,8 @@ static inline int nf_ingress(struct sk_buff *skb, struct packet_type **pt_prev,
return 0;
}
-static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc)
+static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc,
+ struct packet_type **ppt_prev)
{
struct packet_type *ptype, *pt_prev;
rx_handler_func_t *rx_handler;
@@ -4624,8 +4625,7 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc)
if (pt_prev) {
if (unlikely(skb_orphan_frags_rx(skb, GFP_ATOMIC)))
goto drop;
- else
- ret = pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
+ *ppt_prev = pt_prev;
} else {
drop:
if (!deliver_exact)
@@ -4643,6 +4643,18 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc)
return ret;
}
+static int __netif_receive_skb_one_core(struct sk_buff *skb, bool pfmemalloc)
+{
+ struct net_device *orig_dev = skb->dev;
+ struct packet_type *pt_prev = NULL;
+ int ret;
+
+ ret = __netif_receive_skb_core(skb, pfmemalloc, &pt_prev);
+ if (pt_prev)
+ ret = pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
+ return ret;
+}
+
/**
* netif_receive_skb_core - special purpose version of netif_receive_skb
* @skb: buffer to process
@@ -4663,19 +4675,63 @@ int netif_receive_skb_core(struct sk_buff *skb)
int ret;
rcu_read_lock();
- ret = __netif_receive_skb_core(skb, false);
+ ret = __netif_receive_skb_one_core(skb, false);
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL(netif_receive_skb_core);
-static void __netif_receive_skb_list_core(struct list_head *head, bool pfmemalloc)
+static inline void __netif_receive_skb_list_ptype(struct list_head *head,
+ struct packet_type *pt_prev,
+ struct net_device *orig_dev)
{
struct sk_buff *skb, *next;
+ if (!pt_prev)
+ return;
+ if (list_empty(head))
+ return;
+
list_for_each_entry_safe(skb, next, head, list)
- __netif_receive_skb_core(skb, pfmemalloc);
+ pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
+}
+
+static void __netif_receive_skb_list_core(struct list_head *head, bool pfmemalloc)
+{
+ /* Fast-path assumptions:
+ * - There is no RX handler.
+ * - Only one packet_type matches.
+ * If either of these fails, we will end up doing some per-packet
+ * processing in-line, then handling the 'last ptype' for the whole
+ * sublist. This can't cause out-of-order delivery to any single ptype,
+ * because the 'last ptype' must be constant across the sublist, and all
+ * other ptypes are handled per-packet.
+ */
+ /* Current (common) ptype of sublist */
+ struct packet_type *pt_curr = NULL;
+ /* Current (common) orig_dev of sublist */
+ struct net_device *od_curr = NULL;
+ struct list_head sublist;
+ struct sk_buff *skb, *next;
+
+ list_for_each_entry_safe(skb, next, head, list) {
+ struct net_device *orig_dev = skb->dev;
+ struct packet_type *pt_prev = NULL;
+
+ __netif_receive_skb_core(skb, pfmemalloc, &pt_prev);
+ if (pt_curr != pt_prev || od_curr != orig_dev) {
+ /* dispatch old sublist */
+ list_cut_before(&sublist, head, &skb->list);
+ __netif_receive_skb_list_ptype(&sublist, pt_curr, od_curr);
+ /* start new sublist */
+ pt_curr = pt_prev;
+ od_curr = orig_dev;
+ }
+ }
+
+ /* dispatch final sublist */
+ __netif_receive_skb_list_ptype(head, pt_curr, od_curr);
}
static int __netif_receive_skb(struct sk_buff *skb)
@@ -4695,10 +4751,10 @@ static int __netif_receive_skb(struct sk_buff *skb)
* context down to all allocation sites.
*/
noreclaim_flag = memalloc_noreclaim_save();
- ret = __netif_receive_skb_core(skb, true);
+ ret = __netif_receive_skb_one_core(skb, true);
memalloc_noreclaim_restore(noreclaim_flag);
} else
- ret = __netif_receive_skb_core(skb, false);
+ ret = __netif_receive_skb_one_core(skb, false);
return ret;
}
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