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From: Jeff Kirsher on 2 Jun 2010 18:40
From: Alexander Duyck <alexander.h.duyck(a)intel.com>

We can avoid an unecessary cache miss by checking if the skb is non-linear
before accessing gso_size/gso_type in skb_warn_if_lro, the same can also be
done to avoid a cache miss on nr_frags if data_len is 0.

Signed-off-by: Alexander Duyck <alexander.h.duyck(a)intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher(a)intel.com>
---

include/linux/skbuff.h | 3 ++-
net/core/dev.c | 7 ++++---
2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index bf243fc..645e78d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2129,7 +2129,8 @@ static inline bool skb_warn_if_lro(const struct sk_buff *skb)
/* LRO sets gso_size but not gso_type, whereas if GSO is really
* wanted then gso_type will be set. */
struct skb_shared_info *shinfo = skb_shinfo(skb);
- if (shinfo->gso_size != 0 && unlikely(shinfo->gso_type == 0)) {
+ if (skb_is_nonlinear(skb) && shinfo->gso_size != 0 &&
+ unlikely(shinfo->gso_type == 0)) {
__skb_warn_lro_forwarding(skb);
return true;
}
diff --git a/net/core/dev.c b/net/core/dev.c
index d03470f..9f7c407 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2080,9 +2080,10 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
static inline int skb_needs_linearize(struct sk_buff *skb,
struct net_device *dev)
{
- return (skb_has_frags(skb) && !(dev->features & NETIF_F_FRAGLIST)) ||
- (skb_shinfo(skb)->nr_frags && (!(dev->features & NETIF_F_SG) ||
- illegal_highdma(dev, skb)));
+ return skb_is_nonlinear(skb) &&
+ ((skb_has_frags(skb) && !(dev->features & NETIF_F_FRAGLIST)) ||
+ (skb_shinfo(skb)->nr_frags && (!(dev->features & NETIF_F_SG) ||
+ illegal_highdma(dev, skb))));
}

/**

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Prev: How to stop kernel rebooting during startup?
Next: x86: Align skb w/ start of cache line on newer core 2/Xeon Arch