Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750740AbWEOXLZ (ORCPT ); Mon, 15 May 2006 19:11:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750733AbWEOXLZ (ORCPT ); Mon, 15 May 2006 19:11:25 -0400 Received: from smtp-out.google.com ([216.239.45.12]:34072 "EHLO smtp-out.google.com") by vger.kernel.org with ESMTP id S1750717AbWEOXLY (ORCPT ); Mon, 15 May 2006 19:11:24 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=received:date:from:to:cc:subject:in-reply-to:message-id: references:mime-version:content-type; b=jhjicABIkdA63YKJrUClbGJoSfrNY0bkGA7/j/ueG6Cg1SNvHFpmiEkUQSAhimSmU 8ANjEcUpUPPCTeskC3DEA== Date: Mon, 15 May 2006 16:11:05 -0700 (PDT) From: Ranjit Manomohan To: "David S. Miller" cc: ranjitm@google.com, akpm@osdl.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH] tcpdump may trace some outbound packets twice. In-Reply-To: <20060515.142645.94689626.davem@davemloft.net> Message-ID: References: <20060514031034.5d0396e7.akpm@osdl.org> <20060514.134231.101346572.davem@davemloft.net> <20060515.142645.94689626.davem@davemloft.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1976 Lines: 65 On Mon, 15 May 2006, David S. Miller wrote: > From: Ranjit Manomohan > Date: Mon, 15 May 2006 14:19:06 -0700 (PDT) > > > Heres a new version which does a copy instead of the clone to avoid > > the double cloning issue. > > I still very much dislike this patch because it is creating > 1 more clone per packet than is actually necessary and that > is very expensive. > > dev_queue_xmit_nit() is going to clone whatever SKB you send into > there, so better to just bump the reference count (with skb_get()) > instead of cloning or copying. > I was a bit apprehensive about just incrementing the refcnt but that works too. Attached is the modified version. -Thanks, Ranjit --- linux-2.6/net/sched/sch_generic.c 2006-05-10 12:34:52.000000000 -0700 +++ linux/net/sched/sch_generic.c 2006-05-15 15:48:03.000000000 -0700 @@ -136,8 +136,12 @@ if (!netif_queue_stopped(dev)) { int ret; + struct sk_buff *skbc = NULL; + /* Increment the reference count on the skb so + * that we can use it after a successful xmit. + */ if (netdev_nit) - dev_queue_xmit_nit(skb, dev); + skbc = skb_get(skb); ret = dev->hard_start_xmit(skb, dev); if (ret == NETDEV_TX_OK) { @@ -145,9 +149,20 @@ dev->xmit_lock_owner = -1; spin_unlock(&dev->xmit_lock); } + if (skbc) { + /* transmit succeeded, + * trace the buffer. */ + dev_queue_xmit_nit(skbc,dev); + kfree_skb(skbc); + } spin_lock(&dev->queue_lock); return -1; } + + /* Call free in case we incremented refcnt */ + if (skbc) + kfree_skb(skbc); + if (ret == NETDEV_TX_LOCKED && nolock) { spin_lock(&dev->queue_lock); goto collision; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/