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net: reorganize sk_buff for faster __copy_skb_header()

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With proliferation of bit fields in sk_buff, __copy_skb_header() became
quite expensive, showing as the most expensive function in a GSO
workload.

__copy_skb_header() performance is also critical for non GSO TCP
operations, as it is used from skb_clone()

This patch carefully moves all the fields that were not copied in a
separate zone : cloned, nohdr, fclone, peeked, head_frag, xmit_more

Then I moved all other fields and all other copied fields in a section
delimited by headers_start[0]/headers_end[0] section so that we
can use a single memcpy() call, inlined by compiler using long
word load/stores.

I also tried to make all copies in the natural orders of sk_buff,
to help hardware prefetching.

I made sure sk_buff size did not change.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2014-09-28 22:18:47 -07:00
committed by David S. Miller
parent 842abe08aa
commit b193722731
2 changed files with 118 additions and 105 deletions
Download Patch File Download Diff File Expand all files Collapse all files

84
net/core/skbuff.c
View File

@@ -261,7 +261,6 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
atomic_t *fclone_ref = (atomic_t *) (child + 1);
kmemcheck_annotate_bitfield(child, flags1);
kmemcheck_annotate_bitfield(child, flags2);
skb->fclone = SKB_FCLONE_ORIG;
atomic_set(fclone_ref, 1);
@@ -675,57 +674,61 @@ void consume_skb(struct sk_buff *skb)
}
EXPORT_SYMBOL(consume_skb);
/* Make sure a field is enclosed inside headers_start/headers_end section */
#define CHECK_SKB_FIELD(field) \
BUILD_BUG_ON(offsetof(struct sk_buff, field) < \
offsetof(struct sk_buff, headers_start)); \
BUILD_BUG_ON(offsetof(struct sk_buff, field) > \
offsetof(struct sk_buff, headers_end)); \
static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
{
new->tstamp = old->tstamp;
/* We do not copy old->sk */
new->dev = old->dev;
new->transport_header = old->transport_header;
new->network_header = old->network_header;
new->mac_header = old->mac_header;
new->inner_protocol = old->inner_protocol;
new->inner_transport_header = old->inner_transport_header;
new->inner_network_header = old->inner_network_header;
new->inner_mac_header = old->inner_mac_header;
memcpy(new->cb, old->cb, sizeof(old->cb));
skb_dst_copy(new, old);
skb_copy_hash(new, old);
new->ooo_okay = old->ooo_okay;
new->no_fcs = old->no_fcs;
new->encapsulation = old->encapsulation;
new->encap_hdr_csum = old->encap_hdr_csum;
new->csum_valid = old->csum_valid;
new->csum_complete_sw = old->csum_complete_sw;
#ifdef CONFIG_XFRM
new->sp = secpath_get(old->sp);
#endif
memcpy(new->cb, old->cb, sizeof(old->cb));
new->csum = old->csum;
new->ignore_df = old->ignore_df;
new->pkt_type = old->pkt_type;
new->ip_summed = old->ip_summed;
skb_copy_queue_mapping(new, old);
new->priority = old->priority;
#if IS_ENABLED(CONFIG_IP_VS)
new->ipvs_property = old->ipvs_property;
#endif
new->pfmemalloc = old->pfmemalloc;
new->protocol = old->protocol;
new->mark = old->mark;
new->skb_iif = old->skb_iif;
__nf_copy(new, old);
#ifdef CONFIG_NET_SCHED
new->tc_index = old->tc_index;
#ifdef CONFIG_NET_CLS_ACT
new->tc_verd = old->tc_verd;
#endif
#endif
new->vlan_proto = old->vlan_proto;
new->vlan_tci = old->vlan_tci;
__nf_copy(new, old, false);
skb_copy_secmark(new, old);
/* Note : this field could be in headers_start/headers_end section
* It is not yet because we do not want to have a 16 bit hole
*/
new->queue_mapping = old->queue_mapping;
memcpy(&new->headers_start, &old->headers_start,
offsetof(struct sk_buff, headers_end) -
offsetof(struct sk_buff, headers_start));
CHECK_SKB_FIELD(protocol);
CHECK_SKB_FIELD(csum);
CHECK_SKB_FIELD(hash);
CHECK_SKB_FIELD(priority);
CHECK_SKB_FIELD(skb_iif);
CHECK_SKB_FIELD(vlan_proto);
CHECK_SKB_FIELD(vlan_tci);
CHECK_SKB_FIELD(transport_header);
CHECK_SKB_FIELD(network_header);
CHECK_SKB_FIELD(mac_header);
CHECK_SKB_FIELD(inner_protocol);
CHECK_SKB_FIELD(inner_transport_header);
CHECK_SKB_FIELD(inner_network_header);
CHECK_SKB_FIELD(inner_mac_header);
CHECK_SKB_FIELD(mark);
#ifdef CONFIG_NETWORK_SECMARK
CHECK_SKB_FIELD(secmark);
#endif
#ifdef CONFIG_NET_RX_BUSY_POLL
new->napi_id = old->napi_id;
CHECK_SKB_FIELD(napi_id);
#endif
#ifdef CONFIG_NET_SCHED
CHECK_SKB_FIELD(tc_index);
#ifdef CONFIG_NET_CLS_ACT
CHECK_SKB_FIELD(tc_verd);
#endif
#endif
}
/*
@@ -876,7 +879,6 @@ struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
return NULL;
kmemcheck_annotate_bitfield(n, flags1);
kmemcheck_annotate_bitfield(n, flags2);
n->fclone = SKB_FCLONE_UNAVAILABLE;
}