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Commit b1937227 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 842abe08

include/linux/skbuff.h

+72 −61
Original line number Diff line number Diff line
@@ -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;
@@ -3040,11 +3048,13 @@ 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);

	if (copy)

		dst->nfctinfo = src->nfctinfo;

#endif

#ifdef CONFIG_BRIDGE_NETFILTER
@@ -3052,6 +3062,7 @@ static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src) 
	nf_bridge_get(src->nf_bridge);

#endif

#if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE) || defined(CONFIG_NF_TABLES)

	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

net/core/skbuff.c

+41 −39
Original line number Diff line number Diff line
@@ -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;

	}