From dd2d6604407da5b1b260faee409cd601fe914ce9 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Thu, 30 Mar 2023 21:47:31 -0700 Subject: [PATCH] net: minor reshuffle of napi_struct napi_id is read by GRO and drivers to mark skbs, and it currently sits at the end of the structure, in a mostly unused cache line. Move it up into a hole, and separate the clearly control path fields from the important ones. Before: struct napi_struct { struct list_head poll_list; /* 0 16 */ long unsigned int state; /* 16 8 */ int weight; /* 24 4 */ int defer_hard_irqs_count; /* 28 4 */ long unsigned int gro_bitmask; /* 32 8 */ int (*poll)(struct napi_struct *, int); /* 40 8 */ int poll_owner; /* 48 4 */ /* XXX 4 bytes hole, try to pack */ struct net_device * dev; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ struct gro_list gro_hash[8]; /* 64 192 */ /* --- cacheline 4 boundary (256 bytes) --- */ struct sk_buff * skb; /* 256 8 */ struct list_head rx_list; /* 264 16 */ int rx_count; /* 280 4 */ /* XXX 4 bytes hole, try to pack */ struct hrtimer timer; /* 288 64 */ /* XXX last struct has 4 bytes of padding */ /* --- cacheline 5 boundary (320 bytes) was 32 bytes ago --- */ struct list_head dev_list; /* 352 16 */ struct hlist_node napi_hash_node; /* 368 16 */ /* --- cacheline 6 boundary (384 bytes) --- */ unsigned int napi_id; /* 384 4 */ /* XXX 4 bytes hole, try to pack */ struct task_struct * thread; /* 392 8 */ /* size: 400, cachelines: 7, members: 17 */ /* sum members: 388, holes: 3, sum holes: 12 */ /* paddings: 1, sum paddings: 4 */ /* last cacheline: 16 bytes */ }; After: struct napi_struct { struct list_head poll_list; /* 0 16 */ long unsigned int state; /* 16 8 */ int weight; /* 24 4 */ int defer_hard_irqs_count; /* 28 4 */ long unsigned int gro_bitmask; /* 32 8 */ int (*poll)(struct napi_struct *, int); /* 40 8 */ int poll_owner; /* 48 4 */ /* XXX 4 bytes hole, try to pack */ struct net_device * dev; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ struct gro_list gro_hash[8]; /* 64 192 */ /* --- cacheline 4 boundary (256 bytes) --- */ struct sk_buff * skb; /* 256 8 */ struct list_head rx_list; /* 264 16 */ int rx_count; /* 280 4 */ unsigned int napi_id; /* 284 4 */ struct hrtimer timer; /* 288 64 */ /* XXX last struct has 4 bytes of padding */ /* --- cacheline 5 boundary (320 bytes) was 32 bytes ago --- */ struct task_struct * thread; /* 352 8 */ struct list_head dev_list; /* 360 16 */ struct hlist_node napi_hash_node; /* 376 16 */ /* size: 392, cachelines: 7, members: 17 */ /* sum members: 388, holes: 1, sum holes: 4 */ /* paddings: 1, sum paddings: 4 */ /* forced alignments: 1 */ /* last cacheline: 8 bytes */ } __attribute__((__aligned__(8))); Signed-off-by: Jakub Kicinski Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/netdevice.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index c8c634091a65..62e093a6d6d1 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -367,11 +367,12 @@ struct napi_struct { struct sk_buff *skb; struct list_head rx_list; /* Pending GRO_NORMAL skbs */ int rx_count; /* length of rx_list */ + unsigned int napi_id; struct hrtimer timer; + struct task_struct *thread; + /* control-path-only fields follow */ struct list_head dev_list; struct hlist_node napi_hash_node; - unsigned int napi_id; - struct task_struct *thread; }; enum { -- 2.11.0