| Message ID | 20220707191846.1020689-1-edumazet@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | c2dd4059dc31ee6f5b83c8d2064bb1f1f465bcec |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next] net: minor optimization in __alloc_skb() | expand |
Hello: This patch was applied to netdev/net-next.git (master) by David S. Miller <davem@davemloft.net>: On Thu, 7 Jul 2022 19:18:46 +0000 you wrote: > TCP allocates 'fast clones' skbs for packets in tx queues. > > Currently, __alloc_skb() initializes the companion fclone > field to SKB_FCLONE_CLONE, and leaves other fields untouched. > > It makes sense to defer this init much later in skb_clone(), > because all fclone fields are copied and hot in cpu caches > at that time. > > [...] Here is the summary with links: - [net-next] net: minor optimization in __alloc_skb() https://git.kernel.org/netdev/net-next/c/c2dd4059dc31 You are awesome, thank you!
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index c62e42d0c5310caaa03298a779974050b8e58658..c4a7517815815d136dab5576d6b8fa52057002b1 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -454,8 +454,6 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, skb->fclone = SKB_FCLONE_ORIG; refcount_set(&fclones->fclone_ref, 1); - - fclones->skb2.fclone = SKB_FCLONE_CLONE; } return skb; @@ -1513,6 +1511,7 @@ struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask) refcount_read(&fclones->fclone_ref) == 1) { n = &fclones->skb2; refcount_set(&fclones->fclone_ref, 2); + n->fclone = SKB_FCLONE_CLONE; } else { if (skb_pfmemalloc(skb)) gfp_mask |= __GFP_MEMALLOC;
TCP allocates 'fast clones' skbs for packets in tx queues. Currently, __alloc_skb() initializes the companion fclone field to SKB_FCLONE_CLONE, and leaves other fields untouched. It makes sense to defer this init much later in skb_clone(), because all fclone fields are copied and hot in cpu caches at that time. This removes one cache line miss in __alloc_skb(), cost seen on an host with 256 cpus all competing on memory accesses. Signed-off-by: Eric Dumazet <edumazet@google.com> --- net/core/skbuff.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)