All of lore.kernel.org
 help / color / mirror / Atom feed
From: Herbert Xu <herbert@gondor.apana.org.au>
To: "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org
Subject: [PATCH 9/14] gro: Avoid unnecessary comparison after skb_gro_header
Date: Wed, 27 May 2009 14:50:28 +1000	[thread overview]
Message-ID: <E1M9B5w-0001Sn-Oi@gondolin.me.apana.org.au> (raw)
In-Reply-To: 20090527044539.GA32372@gondor.apana.org.au

gro: Avoid unnecessary comparison after skb_gro_header

For the overwhelming majority of cases, skb_gro_header's return
value cannot be NULL.  Yet we must check it because of its current
form.  This patch splits it up into multiple functions in order
to avoid this.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 include/linux/netdevice.h |   23 ++++++++++++++---------
 net/core/dev.c            |   17 ++++++++++++-----
 net/ipv4/af_inet.c        |   13 ++++++++++---
 net/ipv4/tcp.c            |   22 ++++++++++++++++------
 net/ipv6/af_inet6.c       |   13 ++++++++++---
 5 files changed, 62 insertions(+), 26 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 966c413..d2b1561 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1132,18 +1132,23 @@ static inline void skb_gro_pull(struct sk_buff *skb, unsigned int len)
 	NAPI_GRO_CB(skb)->data_offset += len;
 }
 
-static inline void *skb_gro_header(struct sk_buff *skb, unsigned int hlen)
+static inline void *skb_gro_header_fast(struct sk_buff *skb,
+					unsigned int offset)
 {
-	unsigned int offset = skb_gro_offset(skb);
+	return NAPI_GRO_CB(skb)->frag0 + offset;
+}
 
-	hlen += offset;
-	if (NAPI_GRO_CB(skb)->frag0_len < hlen) {
-		NAPI_GRO_CB(skb)->frag0 = NULL;
-		NAPI_GRO_CB(skb)->frag0_len = 0;
-		return pskb_may_pull(skb, hlen) ? skb->data + offset : NULL;
-	}
+static inline int skb_gro_header_hard(struct sk_buff *skb, unsigned int hlen)
+{
+	return NAPI_GRO_CB(skb)->frag0_len < hlen;
+}
 
-	return NAPI_GRO_CB(skb)->frag0 + offset;
+static inline void *skb_gro_header_slow(struct sk_buff *skb, unsigned int hlen,
+					unsigned int offset)
+{
+	NAPI_GRO_CB(skb)->frag0 = NULL;
+	NAPI_GRO_CB(skb)->frag0_len = 0;
+	return pskb_may_pull(skb, hlen) ? skb->data + offset : NULL;
 }
 
 static inline void *skb_gro_mac_header(struct sk_buff *skb)
diff --git a/net/core/dev.c b/net/core/dev.c
index e634c8a..5a81302 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2587,17 +2587,24 @@ struct sk_buff *napi_frags_skb(struct napi_struct *napi)
 {
 	struct sk_buff *skb = napi->skb;
 	struct ethhdr *eth;
+	unsigned int hlen;
+	unsigned int off;
 
 	napi->skb = NULL;
 
 	skb_reset_mac_header(skb);
 	skb_gro_reset_offset(skb);
 
-	eth = skb_gro_header(skb, sizeof(*eth));
-	if (!eth) {
-		napi_reuse_skb(napi, skb);
-		skb = NULL;
-		goto out;
+	off = skb_gro_offset(skb);
+	hlen = off + sizeof(*eth);
+	eth = skb_gro_header_fast(skb, off);
+	if (skb_gro_header_hard(skb, hlen)) {
+		eth = skb_gro_header_slow(skb, hlen, off);
+		if (unlikely(!eth)) {
+			napi_reuse_skb(napi, skb);
+			skb = NULL;
+			goto out;
+		}
 	}
 
 	skb_gro_pull(skb, sizeof(*eth));
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 1706896..644cc55 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1246,13 +1246,20 @@ static struct sk_buff **inet_gro_receive(struct sk_buff **head,
 	struct sk_buff **pp = NULL;
 	struct sk_buff *p;
 	struct iphdr *iph;
+	unsigned int hlen;
+	unsigned int off;
 	int flush = 1;
 	int proto;
 	int id;
 
-	iph = skb_gro_header(skb, sizeof(*iph));
-	if (unlikely(!iph))
-		goto out;
+	off = skb_gro_offset(skb);
+	hlen = off + sizeof(*iph);
+	iph = skb_gro_header_fast(skb, off);
+	if (skb_gro_header_hard(skb, hlen)) {
+		iph = skb_gro_header_slow(skb, hlen, off);
+		if (unlikely(!iph))
+			goto out;
+	}
 
 	proto = iph->protocol & (MAX_INET_PROTOS - 1);
 
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 68342d4..c3dcec5 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2518,20 +2518,30 @@ struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 	unsigned int thlen;
 	unsigned int flags;
 	unsigned int mss = 1;
+	unsigned int hlen;
+	unsigned int off;
 	int flush = 1;
 	int i;
 
-	th = skb_gro_header(skb, sizeof(*th));
-	if (unlikely(!th))
-		goto out;
+	off = skb_gro_offset(skb);
+	hlen = off + sizeof(*th);
+	th = skb_gro_header_fast(skb, off);
+	if (skb_gro_header_hard(skb, hlen)) {
+		th = skb_gro_header_slow(skb, hlen, off);
+		if (unlikely(!th))
+			goto out;
+	}
 
 	thlen = th->doff * 4;
 	if (thlen < sizeof(*th))
 		goto out;
 
-	th = skb_gro_header(skb, thlen);
-	if (unlikely(!th))
-		goto out;
+	hlen = off + thlen;
+	if (skb_gro_header_hard(skb, hlen)) {
+		th = skb_gro_header_slow(skb, hlen, off);
+		if (unlikely(!th))
+			goto out;
+	}
 
 	skb_gro_pull(skb, thlen);
 
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 61f5538..b6215be 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -817,13 +817,20 @@ static struct sk_buff **ipv6_gro_receive(struct sk_buff **head,
 	struct sk_buff *p;
 	struct ipv6hdr *iph;
 	unsigned int nlen;
+	unsigned int hlen;
+	unsigned int off;
 	int flush = 1;
 	int proto;
 	__wsum csum;
 
-	iph = skb_gro_header(skb, sizeof(*iph));
-	if (unlikely(!iph))
-		goto out;
+	off = skb_gro_offset(skb);
+	hlen = off + sizeof(*iph);
+	iph = skb_gro_header_fast(skb, off);
+	if (skb_gro_header_hard(skb, hlen)) {
+		iph = skb_gro_header_slow(skb, hlen, off);
+		if (unlikely(!iph))
+			goto out;
+	}
 
 	skb_gro_pull(skb, sizeof(*iph));
 	skb_set_transport_header(skb, skb_gro_offset(skb));

  parent reply	other threads:[~2009-05-27  5:07 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-05-27  4:45 [0/14] GRO: Lots of microoptimisations Herbert Xu
2009-05-27  4:50 ` [PATCH 1/14] gro: Open-code frags copy in skb_gro_receive Herbert Xu
2009-05-27  4:50 ` [PATCH 2/14] gro: Inline skb_gro_header and cache frag0 virtual address Herbert Xu
2009-05-27  4:50 ` [PATCH 3/14] gro: Localise offset/headlen in skb_gro_offset Herbert Xu
2009-05-27  4:50 ` [PATCH 4/14] gro: Only use skb_gro_header for completely non-linear packets Herbert Xu
2009-05-27  4:50 ` [PATCH 5/14] tcp: Optimise GRO port comparisons Herbert Xu
2009-05-27  4:50 ` [PATCH 6/14] tcp: Remove unnecessary window comparisons for GRO Herbert Xu
2009-05-27  4:50 ` [PATCH 7/14] tcp: Optimise len/mss comparison Herbert Xu
2009-05-27  4:50 ` [PATCH 8/14] gro: Optimise length comparison in skb_gro_header Herbert Xu
2009-05-27  4:50 ` Herbert Xu [this message]
2009-05-27  4:50 ` [PATCH 10/14] ipv4: Use 32-bit loads for ID and length in GRO Herbert Xu
2009-05-27 18:00   ` Andi Kleen
2009-05-27 21:26     ` Herbert Xu
2009-05-27  4:50 ` [PATCH 11/14] gro: Open-code final pskb_may_pull Herbert Xu
2009-05-27  4:50 ` [PATCH 12/14] gro: Nasty optimisations for page frags in skb_gro_receive Herbert Xu
2009-05-27  4:50 ` [PATCH 13/14] gro: Store shinfo in local variable " Herbert Xu
2009-05-27  4:50 ` [PATCH 14/14] tcp: Do not check flush when comparing options for GRO Herbert Xu
2009-05-27 10:42 ` [0/14] GRO: Lots of microoptimisations David Miller
2009-05-27 17:52 ` Benjamin LaHaise
2009-05-27 23:08   ` Herbert Xu
2009-05-28 15:21     ` Benjamin LaHaise
2009-05-29  9:28       ` Herbert Xu
2009-05-29  9:29         ` Herbert Xu
2009-05-29 16:23           ` Benjamin LaHaise
2009-06-10  5:44             ` Herbert Xu
2009-06-12 16:09               ` Benjamin LaHaise
2009-06-12 23:48                 ` David Miller
2009-06-16 16:35                   ` Benjamin LaHaise
2009-06-16 16:38                     ` Herbert Xu
2009-06-17  8:07                       ` Herbert Xu
2009-06-17  8:08                         ` Herbert Xu
2009-06-17 20:14                           ` Rick Jones

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=E1M9B5w-0001Sn-Oi@gondolin.me.apana.org.au \
    --to=herbert@gondor.apana.org.au \
    --cc=davem@davemloft.net \
    --cc=netdev@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.