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net: optimize INET input path further

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Followup of commit b178bb3dfc (net: reorder struct sock fields)

Optimize INET input path a bit further, by :

1) moving sk_refcnt close to sk_lock.

This reduces number of dirtied cache lines by one on 64bit arches (and
64 bytes cache line size).

2) moving inet_daddr & inet_rcv_saddr at the beginning of sk

(same cache line than hash / family / bound_dev_if / nulls_node)

This reduces number of accessed cache lines in lookups by one, and dont
increase size of inet and timewait socks.
inet and tw sockets now share same place-holder for these fields.

Before patch :

offsetof(struct sock, sk_refcnt) = 0x10
offsetof(struct sock, sk_lock) = 0x40
offsetof(struct sock, sk_receive_queue) = 0x60
offsetof(struct inet_sock, inet_daddr) = 0x270
offsetof(struct inet_sock, inet_rcv_saddr) = 0x274

After patch :

offsetof(struct sock, sk_refcnt) = 0x44
offsetof(struct sock, sk_lock) = 0x48
offsetof(struct sock, sk_receive_queue) = 0x68
offsetof(struct inet_sock, inet_daddr) = 0x0
offsetof(struct inet_sock, inet_rcv_saddr) = 0x4

compute_score() (udp or tcp) now use a single cache line per ignored
item, instead of two.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2010-11-30 19:04:07 +00:00
committed by David S. Miller
parent defb3519a6
commit 68835aba4d
6 changed files with 45 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

37
include/net/sock.h
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@ -105,10 +105,8 @@ struct net;
/**
* struct sock_common - minimal network layer representation of sockets
* @skc_node: main hash linkage for various protocol lookup tables
* @skc_nulls_node: main hash linkage for TCP/UDP/UDP-Lite protocol
* @skc_refcnt: reference count
* @skc_tx_queue_mapping: tx queue number for this connection
* @skc_daddr: Foreign IPv4 addr
* @skc_rcv_saddr: Bound local IPv4 addr
* @skc_hash: hash value used with various protocol lookup tables
* @skc_u16hashes: two u16 hash values used by UDP lookup tables
* @skc_family: network address family
@ -119,20 +117,20 @@ struct net;
* @skc_portaddr_node: second hash linkage for UDP/UDP-Lite protocol
* @skc_prot: protocol handlers inside a network family
* @skc_net: reference to the network namespace of this socket
* @skc_node: main hash linkage for various protocol lookup tables
* @skc_nulls_node: main hash linkage for TCP/UDP/UDP-Lite protocol
* @skc_tx_queue_mapping: tx queue number for this connection
* @skc_refcnt: reference count
*
* This is the minimal network layer representation of sockets, the header
* for struct sock and struct inet_timewait_sock.
*/
struct sock_common {
/*
* first fields are not copied in sock_copy()
/* skc_daddr and skc_rcv_saddr must be grouped :
* cf INET_MATCH() and INET_TW_MATCH()
*/
union {
struct hlist_node skc_node;
struct hlist_nulls_node skc_nulls_node;
};
atomic_t skc_refcnt;
int skc_tx_queue_mapping;
__be32 skc_daddr;
__be32 skc_rcv_saddr;
union {
unsigned int skc_hash;
@ -150,6 +148,18 @@ struct sock_common {
#ifdef CONFIG_NET_NS
struct net *skc_net;
#endif
/*
* fields between dontcopy_begin/dontcopy_end
* are not copied in sock_copy()
*/
int skc_dontcopy_begin[0];
union {
struct hlist_node skc_node;
struct hlist_nulls_node skc_nulls_node;
};
int skc_tx_queue_mapping;
atomic_t skc_refcnt;
int skc_dontcopy_end[0];
};
/**
@ -232,7 +242,8 @@ struct sock {
#define sk_refcnt __sk_common.skc_refcnt
#define sk_tx_queue_mapping __sk_common.skc_tx_queue_mapping
#define sk_copy_start __sk_common.skc_hash
#define sk_dontcopy_begin __sk_common.skc_dontcopy_begin
#define sk_dontcopy_end __sk_common.skc_dontcopy_end
#define sk_hash __sk_common.skc_hash
#define sk_family __sk_common.skc_family
#define sk_state __sk_common.skc_state