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 <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 8eaa624..b6cced3 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -527,27 +527,41 @@
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
@@ -558,28 +572,33 @@
#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;
+ __u8 pkt_type:3;
+ __u8 pfmemalloc:1;
+ __u8 ignore_df:1;
+ __u8 nfctinfo:3;
- void (*destructor)(struct sk_buff *skb);
-#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
- struct nf_conntrack *nfct;
+ __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;
+ /* 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;
+ __u8 csum_level:2;
+ __u8 csum_bad:1;
+
+#ifdef CONFIG_IPV6_NDISC_NODETYPE
+ __u8 ndisc_nodetype:2;
#endif
-#ifdef CONFIG_BRIDGE_NETFILTER
- struct nf_bridge_info *nf_bridge;
-#endif
-
- int skb_iif;
-
- __u32 hash;
-
- __be16 vlan_proto;
- __u16 vlan_tci;
+ __u8 ipvs_property:1;
+ /* 5 or 7 bit hole */
#ifdef CONFIG_NET_SCHED
__u16 tc_index; /* traffic control index */
@@ -588,28 +607,18 @@
#endif
#endif
- __u16 queue_mapping;
- kmemcheck_bitfield_begin(flags2);
- __u8 xmit_more:1;
-#ifdef CONFIG_IPV6_NDISC_NODETYPE
- __u8 ndisc_nodetype:2;
-#endif
- __u8 pfmemalloc:1;
- __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);
-
+ 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 @@
__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 @@
}
/* 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 @@
#ifdef CONFIG_BRIDGE_NETFILTER
nf_bridge_put(dst->nf_bridge);
#endif
- __nf_copy(dst, src);
+ __nf_copy(dst, src, true);
}
#ifdef CONFIG_NETWORK_SECMARK