From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: getting warn once around skb_try_coalesce Date: Tue, 10 Jul 2012 13:14:08 +0200 Message-ID: <1341918848.3265.4853.camel@edumazet-glaptop> References: <4FFBFBD2.6030004@mellanox.com> <1341915510.3265.4734.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: David Miller , "netdev@vger.kernel.org" , Shlomo Pongratz , Erez Shitrit To: Or Gerlitz Return-path: Received: from mail-ee0-f46.google.com ([74.125.83.46]:54796 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754720Ab2GJLOM (ORCPT ); Tue, 10 Jul 2012 07:14:12 -0400 Received: by eeit10 with SMTP id t10so4633604eei.19 for ; Tue, 10 Jul 2012 04:14:11 -0700 (PDT) In-Reply-To: <1341915510.3265.4734.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 2012-07-10 at 12:18 +0200, Eric Dumazet wrote: > On Tue, 2012-07-10 at 12:54 +0300, Or Gerlitz wrote: > > Hi Dave, Eric, > > > > Another trace that I see here with net-next is this one-time warning. I > > get it always > > on the passive side of TCP, something that seems related to GRO, it > > happens only with > > IPoIB, not with mlx4_en and igb (when igb get to work on net-next...) > > > > The latest commit in this area is bad43ca8325f493dcaa0896c2f036276af059c7e > > "net: introduce skb_try_coalesce()" from Eric. > > > > Or. > > > > -----------[ cut here ]------------ > > WARNING: at net/core/skbuff.c:3413 skb_try_coalesce+0x1f8/0x31d() > > This warning catch skb truesize offenders, most probably its a driver > issue. > By the way, this driver allocates not enough tailroom in skbs, so IP/TCP stacks need to reallocate skb head to pull IP/TCP headers. Thats not efficient. I suggest using following patch : diff --git a/drivers/infiniband/ulp/ipoib/ipoib_ib.c b/drivers/infiniband/ulp/ipoib/ipoib_ib.c index 5c1bc99..9939869 100644 --- a/drivers/infiniband/ulp/ipoib/ipoib_ib.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_ib.c @@ -159,7 +159,7 @@ static struct sk_buff *ipoib_alloc_rx_skb(struct net_device *dev, int id) u64 *mapping; if (ipoib_ud_need_sg(priv->max_ib_mtu)) - buf_size = IPOIB_UD_HEAD_SIZE; + buf_size = IPOIB_UD_HEAD_SIZE + 128; /* reserve some tailroom for IP/TCP headers */ else buf_size = IPOIB_UD_BUF_SIZE(priv->max_ib_mtu);