From 8a29111c7ca68d928dfab58636f3f6acf0ac04f7 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 8 Oct 2013 09:02:23 -0700 Subject: [PATCH] net: gro: allow to build full sized skb skb_gro_receive() is currently limited to 16 or 17 MSS per GRO skb, typically 24616 bytes, because it fills up to MAX_SKB_FRAGS frags. It's relatively easy to extend the skb using frag_list to allow more frags to be appended into the last sk_buff. This still builds very efficient skbs, and allows reaching 45 MSS per skb. (45 MSS GRO packet uses one skb plus a frag_list containing 2 additional sk_buff) High speed TCP flows benefit from this extension by lowering TCP stack cpu usage (less packets stored in receive queue, less ACK packets processed) Forwarding setups could be hurt, as such skbs will need to be linearized, although its not a new problem, as GRO could already provide skbs with a frag_list. We could make the 65536 bytes threshold a tunable to mitigate this. (First time we need to linearize skb in skb_needs_linearize(), we could lower the tunable to ~16*1460 so that following skb_gro_receive() calls build smaller skbs) Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/skbuff.c | 43 ++++++++++++++++++++++++++----------------- 1 file changed, 26 insertions(+), 17 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index d81cff119f73..8ead744fcc94 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2936,32 +2936,30 @@ EXPORT_SYMBOL_GPL(skb_segment); int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb) { - struct sk_buff *p = *head; - struct sk_buff *nskb; - struct skb_shared_info *skbinfo = skb_shinfo(skb); - struct skb_shared_info *pinfo = skb_shinfo(p); - unsigned int headroom; - unsigned int len = skb_gro_len(skb); + struct skb_shared_info *pinfo, *skbinfo = skb_shinfo(skb); unsigned int offset = skb_gro_offset(skb); unsigned int headlen = skb_headlen(skb); + struct sk_buff *nskb, *lp, *p = *head; + unsigned int len = skb_gro_len(skb); unsigned int delta_truesize; + unsigned int headroom; - if (p->len + len >= 65536) + if (unlikely(p->len + len >= 65536)) return -E2BIG; - if (pinfo->frag_list) - goto merge; - else if (headlen <= offset) { + lp = NAPI_GRO_CB(p)->last ?: p; + pinfo = skb_shinfo(lp); + + if (headlen <= offset) { skb_frag_t *frag; skb_frag_t *frag2; int i = skbinfo->nr_frags; int nr_frags = pinfo->nr_frags + i; - offset -= headlen; - if (nr_frags > MAX_SKB_FRAGS) - return -E2BIG; + goto merge; + offset -= headlen; pinfo->nr_frags = nr_frags; skbinfo->nr_frags = 0; @@ -2992,7 +2990,7 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb) unsigned int first_offset; if (nr_frags + 1 + skbinfo->nr_frags > MAX_SKB_FRAGS) - return -E2BIG; + goto merge; first_offset = skb->data - (unsigned char *)page_address(page) + @@ -3010,7 +3008,10 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb) delta_truesize = skb->truesize - SKB_DATA_ALIGN(sizeof(struct sk_buff)); NAPI_GRO_CB(skb)->free = NAPI_GRO_FREE_STOLEN_HEAD; goto done; - } else if (skb_gro_len(p) != pinfo->gso_size) + } + if (pinfo->frag_list) + goto merge; + if (skb_gro_len(p) != pinfo->gso_size) return -E2BIG; headroom = skb_headroom(p); @@ -3062,16 +3063,24 @@ merge: __skb_pull(skb, offset); - NAPI_GRO_CB(p)->last->next = skb; + if (!NAPI_GRO_CB(p)->last) + skb_shinfo(p)->frag_list = skb; + else + NAPI_GRO_CB(p)->last->next = skb; NAPI_GRO_CB(p)->last = skb; skb_header_release(skb); + lp = p; done: NAPI_GRO_CB(p)->count++; p->data_len += len; p->truesize += delta_truesize; p->len += len; - + if (lp != p) { + lp->data_len += len; + lp->truesize += delta_truesize; + lp->len += len; + } NAPI_GRO_CB(skb)->same_flow = 1; return 0; } -- 2.20.1