From b1937227316417aa7568d01e6fa1f272e98fb890 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 28 Sep 2014 22:18:47 -0700 Subject: [PATCH] net: reorganize sk_buff for faster __copy_skb_header() 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 Signed-off-by: David S. Miller --- include/linux/skbuff.h | 133 ++++++++++++++++++++++------------------- net/core/skbuff.c | 80 +++++++++++++------------ 2 files changed, 113 insertions(+), 100 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 8eaa62400fca..b6cced304b26 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -527,27 +527,41 @@ struct sk_buff { char cb[48] __aligned(8); unsigned long _skb_refdst; + void (*destructor)(struct sk_buff *skb); #ifdef CONFIG_XFRM struct sec_path *sp; +#endif +#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE) + struct nf_conntrack *nfct; +#endif +#ifdef CONFIG_BRIDGE_NETFILTER + struct nf_bridge_info *nf_bridge; #endif unsigned int len, data_len; __u16 mac_len, hdr_len; - union { - __wsum csum; - struct { - __u16 csum_start; - __u16 csum_offset; - }; - }; - __u32 priority; + + /* Following fields are _not_ copied in __copy_skb_header() + * Note that queue_mapping is here mostly to fill a hole. + */ kmemcheck_bitfield_begin(flags1); - __u8 ignore_df:1, - cloned:1, - ip_summed:2, + __u16 queue_mapping; + __u8 cloned:1, nohdr:1, - nfctinfo:3; + fclone:2, + peeked:1, + head_frag:1, + xmit_more:1; + /* one bit hole */ + kmemcheck_bitfield_end(flags1); + + + + /* fields enclosed in headers_start/headers_end are copied + * using a single memcpy() in __copy_skb_header() + */ + __u32 headers_start[0]; /* if you move pkt_type around you also must adapt those constants */ #ifdef __BIG_ENDIAN_BITFIELD @@ -558,58 +572,53 @@ struct sk_buff { #define PKT_TYPE_OFFSET() offsetof(struct sk_buff, __pkt_type_offset) __u8 __pkt_type_offset[0]; - __u8 pkt_type:3, - fclone:2, - ipvs_property:1, - peeked:1, - nf_trace:1; - kmemcheck_bitfield_end(flags1); - __be16 protocol; - - void (*destructor)(struct sk_buff *skb); -#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE) - struct nf_conntrack *nfct; -#endif -#ifdef CONFIG_BRIDGE_NETFILTER - struct nf_bridge_info *nf_bridge; -#endif - - int skb_iif; - - __u32 hash; - - __be16 vlan_proto; - __u16 vlan_tci; - -#ifdef CONFIG_NET_SCHED - __u16 tc_index; /* traffic control index */ -#ifdef CONFIG_NET_CLS_ACT - __u16 tc_verd; /* traffic control verdict */ -#endif -#endif - - __u16 queue_mapping; - kmemcheck_bitfield_begin(flags2); - __u8 xmit_more:1; -#ifdef CONFIG_IPV6_NDISC_NODETYPE - __u8 ndisc_nodetype:2; -#endif + __u8 pkt_type:3; __u8 pfmemalloc:1; + __u8 ignore_df:1; + __u8 nfctinfo:3; + + __u8 nf_trace:1; + __u8 ip_summed:2; __u8 ooo_okay:1; __u8 l4_hash:1; __u8 sw_hash:1; __u8 wifi_acked_valid:1; __u8 wifi_acked:1; + __u8 no_fcs:1; - __u8 head_frag:1; /* Indicates the inner headers are valid in the skbuff. */ __u8 encapsulation:1; __u8 encap_hdr_csum:1; __u8 csum_valid:1; __u8 csum_complete_sw:1; - /* 1/3 bit hole (depending on ndisc_nodetype presence) */ - kmemcheck_bitfield_end(flags2); + __u8 csum_level:2; + __u8 csum_bad:1; +#ifdef CONFIG_IPV6_NDISC_NODETYPE + __u8 ndisc_nodetype:2; +#endif + __u8 ipvs_property:1; + /* 5 or 7 bit hole */ + +#ifdef CONFIG_NET_SCHED + __u16 tc_index; /* traffic control index */ +#ifdef CONFIG_NET_CLS_ACT + __u16 tc_verd; /* traffic control verdict */ +#endif +#endif + + union { + __wsum csum; + struct { + __u16 csum_start; + __u16 csum_offset; + }; + }; + __u32 priority; + int skb_iif; + __u32 hash; + __be16 vlan_proto; + __u16 vlan_tci; #if defined CONFIG_NET_DMA || defined CONFIG_NET_RX_BUSY_POLL union { unsigned int napi_id; @@ -625,19 +634,18 @@ struct sk_buff { __u32 reserved_tailroom; }; - kmemcheck_bitfield_begin(flags3); - __u8 csum_level:2; - __u8 csum_bad:1; - /* 13 bit hole */ - kmemcheck_bitfield_end(flags3); - __be16 inner_protocol; __u16 inner_transport_header; __u16 inner_network_header; __u16 inner_mac_header; + + __be16 protocol; __u16 transport_header; __u16 network_header; __u16 mac_header; + + __u32 headers_end[0]; + /* These elements must be at the end, see alloc_skb() for details. */ sk_buff_data_t tail; sk_buff_data_t end; @@ -3040,19 +3048,22 @@ static inline void nf_reset_trace(struct sk_buff *skb) } /* Note: This doesn't put any conntrack and bridge info in dst. */ -static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src) +static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src, + bool copy) { #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE) dst->nfct = src->nfct; nf_conntrack_get(src->nfct); - dst->nfctinfo = src->nfctinfo; + if (copy) + dst->nfctinfo = src->nfctinfo; #endif #ifdef CONFIG_BRIDGE_NETFILTER dst->nf_bridge = src->nf_bridge; nf_bridge_get(src->nf_bridge); #endif #if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE) || defined(CONFIG_NF_TABLES) - dst->nf_trace = src->nf_trace; + if (copy) + dst->nf_trace = src->nf_trace; #endif } @@ -3064,7 +3075,7 @@ static inline void nf_copy(struct sk_buff *dst, const struct sk_buff *src) #ifdef CONFIG_BRIDGE_NETFILTER nf_bridge_put(dst->nf_bridge); #endif - __nf_copy(dst, src); + __nf_copy(dst, src, true); } #ifdef CONFIG_NETWORK_SECMARK diff --git a/net/core/skbuff.c b/net/core/skbuff.c index d4fdc649112c..4be570a4ab21 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -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; + __nf_copy(new, old, false); + + /* 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 + CHECK_SKB_FIELD(napi_id); #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; + CHECK_SKB_FIELD(tc_index); #ifdef CONFIG_NET_CLS_ACT - new->tc_verd = old->tc_verd; + CHECK_SKB_FIELD(tc_verd); #endif #endif - new->vlan_proto = old->vlan_proto; - new->vlan_tci = old->vlan_tci; - - skb_copy_secmark(new, old); -#ifdef CONFIG_NET_RX_BUSY_POLL - new->napi_id = old->napi_id; -#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; } -- 2.30.2