From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH net-next] net_sched: more precise pkt_len computation Date: Fri, 26 Oct 2012 11:32:50 +0200 Message-ID: <1351243970.6537.321.camel@edumazet-glaptop> References: <1350965711-4390-1-git-send-email-amwang@redhat.com> <1350982432.26308.8.camel@cr0> <58DEB62C-6237-435E-8300-8E390F101F58@unimore.it> <1351239007.6537.291.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Stephen Hemminger , Patrick McHardy , Paolo Valente , Jamal Hadi Salim , Herbert Xu To: David Miller Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:48966 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755932Ab2JZJcy (ORCPT ); Fri, 26 Oct 2012 05:32:54 -0400 Received: by mail-bk0-f46.google.com with SMTP id jk13so1165009bkc.19 for ; Fri, 26 Oct 2012 02:32:52 -0700 (PDT) In-Reply-To: <1351239007.6537.291.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet One long standing problem with TSO/GSO/GRO packets is that skb->len doesnt represent a precise amount of bytes on wire. Headers are only accounted for the first segment. For TCP, thats typically 66 bytes per 1448 bytes segment missing, an error of 4.5 % As consequences : 1) TBF/CBQ/HTB/NETEM/... can send more bytes than the assigned limits. 2) Device stats are slightly under estimated as well. Fix this by taking account of headers in qdisc_skb_cb(skb)->pkt_len computation. Packet schedulers should use pkt_len instead of skb->len for their bandwidth limitations, and TSO enabled devices drivers could use pkt_len if their statistics are not hardware assisted, and if they dont scratch skb->cb[] first word. Signed-off-by: Eric Dumazet Cc: Jamal Hadi Salim Cc: Stephen Hemminger Cc: Paolo Valente Cc: Herbert Xu Cc: Patrick McHardy --- net/core/dev.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index b4978e2..cf2b5f4 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2442,7 +2442,6 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q, bool contended; int rc; - qdisc_skb_cb(skb)->pkt_len = skb->len; qdisc_calculate_pkt_len(skb, q); /* * Heuristic to force contended enqueues to serialize on a @@ -2579,6 +2578,16 @@ int dev_queue_xmit(struct sk_buff *skb) skb->tc_verd = SET_TC_AT(skb->tc_verd, AT_EGRESS); #endif trace_net_dev_queue(skb); + qdisc_skb_cb(skb)->pkt_len = skb->len; + if (skb_is_gso(skb)) { + unsigned int hdr_len = skb_transport_offset(skb); + + if (skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)) + hdr_len += tcp_hdrlen(skb); + else + hdr_len += sizeof(struct udphdr); + qdisc_skb_cb(skb)->pkt_len += (skb_shinfo(skb)->gso_segs - 1) * hdr_len; + } if (q->enqueue) { rc = __dev_xmit_skb(skb, q, dev, txq); goto out;