From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Subject: Re: [PATCH net v2] net: pktgen: fix pkt_size Date: Fri, 30 Sep 2016 08:39:20 -0700 Message-ID: <1475249960.3279.1.camel@gmail.com> References: <5277a40b08c491bd4ff8f6e3276718848f7406e8.1475246890.git.pabeni@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, "David S. Miller" , Bogdan Hamciuc , Ben Greear , Sergei Shtylyov To: Paolo Abeni Return-path: Received: from mail-pa0-f66.google.com ([209.85.220.66]:35950 "EHLO mail-pa0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932515AbcI3PjW (ORCPT ); Fri, 30 Sep 2016 11:39:22 -0400 Received: by mail-pa0-f66.google.com with SMTP id cd13so3115257pac.3 for ; Fri, 30 Sep 2016 08:39:22 -0700 (PDT) In-Reply-To: <5277a40b08c491bd4ff8f6e3276718848f7406e8.1475246890.git.pabeni@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 2016-09-30 at 16:56 +0200, Paolo Abeni wrote: > The commit 879c7220e828 ("net: pktgen: Observe needed_headroom > of the device") increased the 'pkt_overhead' field value by > LL_RESERVED_SPACE. > As a side effect the generated packet size, computed as: > > /* Eth + IPh + UDPh + mpls */ > datalen = pkt_dev->cur_pkt_size - 14 - 20 - 8 - > pkt_dev->pkt_overhead; > > is decreased by the same value. > The above changed slightly the behavior of existing pktgen users, > and made the procfs interface somewhat inconsistent. > Fix it by restoring the previous pkt_overhead value and using > LL_RESERVED_SPACE as extralen in skb allocation. > Also, change pktgen_alloc_skb() to only partially reserve > the headroom to allow the caller to prefetch from ll header > start. > > v1 -> v2: > - fixed some typos in the comments > > Fixes: 879c7220e828 ("net: pktgen: Observe needed_headroom of the device") > Suggested-by: Ben Greear > Signed-off-by: Paolo Abeni > --- > net/core/pktgen.c | 21 ++++++++++----------- > 1 file changed, 10 insertions(+), 11 deletions(-) > > diff --git a/net/core/pktgen.c b/net/core/pktgen.c > index bbd118b..5219a9e 100644 > --- a/net/core/pktgen.c > +++ b/net/core/pktgen.c > @@ -2286,7 +2286,7 @@ out: > > static inline void set_pkt_overhead(struct pktgen_dev *pkt_dev) > { > - pkt_dev->pkt_overhead = LL_RESERVED_SPACE(pkt_dev->odev); > + pkt_dev->pkt_overhead = 0; > pkt_dev->pkt_overhead += pkt_dev->nr_labels*sizeof(u32); > pkt_dev->pkt_overhead += VLAN_TAG_SIZE(pkt_dev); > pkt_dev->pkt_overhead += SVLAN_TAG_SIZE(pkt_dev); > @@ -2777,13 +2777,13 @@ static void pktgen_finalize_skb(struct pktgen_dev *pkt_dev, struct sk_buff *skb, > } > > static struct sk_buff *pktgen_alloc_skb(struct net_device *dev, > - struct pktgen_dev *pkt_dev, > - unsigned int extralen) > + struct pktgen_dev *pkt_dev) > { > + unsigned int extralen = LL_RESERVED_SPACE(dev); > struct sk_buff *skb = NULL; > - unsigned int size = pkt_dev->cur_pkt_size + 64 + extralen + > - pkt_dev->pkt_overhead; > + unsigned int size; > > + size = pkt_dev->cur_pkt_size + 64 + extralen + pkt_dev->pkt_overhead; > if (pkt_dev->flags & F_NODE) { > int node = pkt_dev->node >= 0 ? pkt_dev->node : numa_node_id(); > > @@ -2796,8 +2796,9 @@ static struct sk_buff *pktgen_alloc_skb(struct net_device *dev, > skb = __netdev_alloc_skb(dev, size, GFP_NOWAIT); > } > > + /* the caller pre-fetches from skb->data and reserves for the mac hdr */ > if (likely(skb)) > - skb_reserve(skb, LL_RESERVED_SPACE(dev)); > + skb_reserve(skb, extralen - 16); Is the 16 here the same as HD_DATA_MOD? Magic numbers... Thanks, - Greg > > return skb; > } > @@ -2830,16 +2831,14 @@ static struct sk_buff *fill_packet_ipv4(struct net_device *odev, > mod_cur_headers(pkt_dev); > queue_map = pkt_dev->cur_queue_map; > > - datalen = (odev->hard_header_len + 16) & ~0xf; > - > - skb = pktgen_alloc_skb(odev, pkt_dev, datalen); > + skb = pktgen_alloc_skb(odev, pkt_dev); > if (!skb) { > sprintf(pkt_dev->result, "No memory"); > return NULL; > } > > prefetchw(skb->data); > - skb_reserve(skb, datalen); > + skb_reserve(skb, 16); > > /* Reserve for ethernet and IP header */ > eth = (__u8 *) skb_push(skb, 14); > @@ -2959,7 +2958,7 @@ static struct sk_buff *fill_packet_ipv6(struct net_device *odev, > mod_cur_headers(pkt_dev); > queue_map = pkt_dev->cur_queue_map; > > - skb = pktgen_alloc_skb(odev, pkt_dev, 16); > + skb = pktgen_alloc_skb(odev, pkt_dev); > if (!skb) { > sprintf(pkt_dev->result, "No memory"); > return NULL;