• Eric Dumazet's avatar
    net: reorganize struct sock for better data locality · 9115e8cd
    Eric Dumazet authored
    
    
    Group fields used in TX path, and keep some cache lines mostly read
    to permit sharing among cpus.
    
    Gained two 4 bytes holes on 64bit arches.
    
    Added a place holder for tcp tsq_flags, next to sk_wmem_alloc
    to speed up tcp_wfree() in the following patch.
    
    I have not added ____cacheline_aligned_in_smp, this might be done later.
    I prefer doing this once inet and tcp/udp sockets reorg is also done.
    
    Tested with both TCP and UDP.
    
    UDP receiver performance under flood increased by ~20 % :
    Accessing sk_filter/sk_wq/sk_napi_id no longer stalls because sk_drops
    was moved away from a critical cache line, now mostly read and shared.
    
    	/* --- cacheline 4 boundary (256 bytes) --- */
    	unsigned int               sk_napi_id;           /* 0x100   0x4 */
    	int                        sk_rcvbuf;            /* 0x104   0x4 */
    	struct sk_filter *         sk_filter;            /* 0x108   0x8 */
    	union {
    		struct socket_wq * sk_wq;                /*         0x8 */
    		struct socket_wq * sk_wq_raw;            /*         0x8 */
    	};                                               /* 0x110   0x8 */
    	struct xfrm_policy *       sk_policy[2];         /* 0x118  0x10 */
    	struct dst_entry *         sk_rx_dst;            /* 0x128   0x8 */
    	struct dst_entry *         sk_dst_cache;         /* 0x130   0x8 */
    	atomic_t                   sk_omem_alloc;        /* 0x138   0x4 */
    	int                        sk_sndbuf;            /* 0x13c   0x4 */
    	/* --- cacheline 5 boundary (320 bytes) --- */
    	int                        sk_wmem_queued;       /* 0x140   0x4 */
    	atomic_t                   sk_wmem_alloc;        /* 0x144   0x4 */
    	long unsigned int          sk_tsq_flags;         /* 0x148   0x8 */
    	struct sk_buff *           sk_send_head;         /* 0x150   0x8 */
    	struct sk_buff_head        sk_write_queue;       /* 0x158  0x18 */
    	__s32                      sk_peek_off;          /* 0x170   0x4 */
    	int                        sk_write_pending;     /* 0x174   0x4 */
    	long int                   sk_sndtimeo;          /* 0x178   0x8 */
    
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Tested-by: default avatarPaolo Abeni <pabeni@redhat.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    9115e8cd