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net-gro: restore frag0 optimization 

Main difference between napi_frags_skb() and napi_gro_receive() is that
the later is called while ethernet header was already pulled by the NIC
driver (eth_type_trans() was called before napi_gro_receive())

Jerry Chu in commit 299603e837 ("net-gro: Prepare GRO stack for the
upcoming tunneling support") tried to remove this difference by calling
eth_type_trans() from napi_frags_skb() instead of doing this later from
napi_frags_finish()

Goal was that napi_gro_complete() could call
ptype->callbacks.gro_complete(skb, 0)  (offset of first network header =
0)

Also, xxx_gro_receive() handlers all use off = skb_gro_offset(skb) to
point to their own header, for the current skb and ones held in gro_list

Problem is this cleanup work defeated the frag0 optimization:
It turns out the consecutive pskb_may_pull() calls are too expensive.

This patch brings back the frag0 stuff in napi_frags_skb().

As all skb have their mac header in skb head, we no longer need
skb_gro_mac_header()

Reported-by: Michal Schmidt <mschmidt@redhat.com>
Fixes: 299603e837 ("net-gro: Prepare GRO stack for the upcoming tunneling support")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jerry Chu <hkchu@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2014-03-29 21:28:21 -07:00 committed by David S. Miller
parent bf39b4247b
commit a50e233c50
2 changed files with 64 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/netdevice.h
View File

@ -2014,11 +2014,6 @@ static inline void *skb_gro_header_slow(struct sk_buff *skb, unsigned int hlen,
return skb->data + offset;
}
static inline void *skb_gro_mac_header(struct sk_buff *skb)
{
return NAPI_GRO_CB(skb)->frag0 ?: skb_mac_header(skb);
}
static inline void *skb_gro_network_header(struct sk_buff *skb)
{
return (NAPI_GRO_CB(skb)->frag0 ?: skb->data) +

96
net/core/dev.c
View File

@ -3833,10 +3833,10 @@ static void gro_list_prepare(struct napi_struct *napi, struct sk_buff *skb)
diffs |= p->vlan_tci ^ skb->vlan_tci;
if (maclen == ETH_HLEN)
diffs |= compare_ether_header(skb_mac_header(p),
skb_gro_mac_header(skb));
skb_mac_header(skb));
else if (!diffs)
diffs = memcmp(skb_mac_header(p),
skb_gro_mac_header(skb),
skb_mac_header(skb),
maclen);
NAPI_GRO_CB(p)->same_flow = !diffs;
}
@ -3859,6 +3859,27 @@ static void skb_gro_reset_offset(struct sk_buff *skb)
}
}
static void gro_pull_from_frag0(struct sk_buff *skb, int grow)
{
struct skb_shared_info *pinfo = skb_shinfo(skb);
BUG_ON(skb->end - skb->tail < grow);
memcpy(skb_tail_pointer(skb), NAPI_GRO_CB(skb)->frag0, grow);
skb->data_len -= grow;
skb->tail += grow;
pinfo->frags[0].page_offset += grow;
skb_frag_size_sub(&pinfo->frags[0], grow);
if (unlikely(!skb_frag_size(&pinfo->frags[0]))) {
skb_frag_unref(skb, 0);
memmove(pinfo->frags, pinfo->frags + 1,
--pinfo->nr_frags * sizeof(pinfo->frags[0]));
}
}
static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff *skb)
{
struct sk_buff **pp = NULL;
@ -3867,6 +3888,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
struct list_head *head = &offload_base;
int same_flow;
enum gro_result ret;
int grow;
if (!(skb->dev->features & NETIF_F_GRO))
goto normal;
@ -3874,7 +3896,6 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
if (skb_is_gso(skb) || skb_has_frag_list(skb))
goto normal;
skb_gro_reset_offset(skb);
gro_list_prepare(napi, skb);
NAPI_GRO_CB(skb)->csum = skb->csum; /* Needed for CHECKSUM_COMPLETE */
@ -3938,27 +3959,9 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
ret = GRO_HELD;
pull:
if (skb_headlen(skb) < skb_gro_offset(skb)) {
int grow = skb_gro_offset(skb) - skb_headlen(skb);
BUG_ON(skb->end - skb->tail < grow);
memcpy(skb_tail_pointer(skb), NAPI_GRO_CB(skb)->frag0, grow);
skb->tail += grow;
skb->data_len -= grow;
skb_shinfo(skb)->frags[0].page_offset += grow;
skb_frag_size_sub(&skb_shinfo(skb)->frags[0], grow);
if (unlikely(!skb_frag_size(&skb_shinfo(skb)->frags[0]))) {
skb_frag_unref(skb, 0);
memmove(skb_shinfo(skb)->frags,
skb_shinfo(skb)->frags + 1,
--skb_shinfo(skb)->nr_frags * sizeof(skb_frag_t));
}
}
grow = skb_gro_offset(skb) - skb_headlen(skb);
if (grow > 0)
gro_pull_from_frag0(skb, grow);
ok:
return ret;
@ -4026,6 +4029,8 @@ gro_result_t napi_gro_receive(struct napi_struct *napi, struct sk_buff *skb)
{
trace_napi_gro_receive_entry(skb);
skb_gro_reset_offset(skb);
return napi_skb_finish(dev_gro_receive(napi, skb), skb);
}
EXPORT_SYMBOL(napi_gro_receive);
@ -4054,12 +4059,16 @@ struct sk_buff *napi_get_frags(struct napi_struct *napi)
}
EXPORT_SYMBOL(napi_get_frags);
static gro_result_t napi_frags_finish(struct napi_struct *napi, struct sk_buff *skb,
gro_result_t ret)
static gro_result_t napi_frags_finish(struct napi_struct *napi,
struct sk_buff *skb,
gro_result_t ret)
{
switch (ret) {
case GRO_NORMAL:
if (netif_receive_skb_internal(skb))
case GRO_HELD:
__skb_push(skb, ETH_HLEN);
skb->protocol = eth_type_trans(skb, skb->dev);
if (ret == GRO_NORMAL && netif_receive_skb_internal(skb))
ret = GRO_DROP;
break;
@ -4068,7 +4077,6 @@ static gro_result_t napi_frags_finish(struct napi_struct *napi, struct sk_buff *
napi_reuse_skb(napi, skb);
break;
case GRO_HELD:
case GRO_MERGED:
break;
}
@ -4076,17 +4084,41 @@ static gro_result_t napi_frags_finish(struct napi_struct *napi, struct sk_buff *
return ret;
}
/* Upper GRO stack assumes network header starts at gro_offset=0
* Drivers could call both napi_gro_frags() and napi_gro_receive()
* We copy ethernet header into skb->data to have a common layout.
*/
static struct sk_buff *napi_frags_skb(struct napi_struct *napi)
{
struct sk_buff *skb = napi->skb;
const struct ethhdr *eth;
unsigned int hlen = sizeof(*eth);
napi->skb = NULL;
if (unlikely(!pskb_may_pull(skb, sizeof(struct ethhdr)))) {
napi_reuse_skb(napi, skb);
return NULL;
skb_reset_mac_header(skb);
skb_gro_reset_offset(skb);
eth = skb_gro_header_fast(skb, 0);
if (unlikely(skb_gro_header_hard(skb, hlen))) {
eth = skb_gro_header_slow(skb, hlen, 0);
if (unlikely(!eth)) {
napi_reuse_skb(napi, skb);
return NULL;
}
} else {
gro_pull_from_frag0(skb, hlen);
NAPI_GRO_CB(skb)->frag0 += hlen;
NAPI_GRO_CB(skb)->frag0_len -= hlen;
}
skb->protocol = eth_type_trans(skb, skb->dev);
__skb_pull(skb, hlen);
/*
* This works because the only protocols we care about don't require
* special handling.
* We'll fix it up properly in napi_frags_finish()
*/
skb->protocol = eth->h_proto;
return skb;
}