From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754578AbbIPR7j (ORCPT ); Wed, 16 Sep 2015 13:59:39 -0400 Received: from shards.monkeyblade.net ([149.20.54.216]:33861 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754473AbbIPR7h (ORCPT ); Wed, 16 Sep 2015 13:59:37 -0400 Date: Wed, 16 Sep 2015 10:59:36 -0700 (PDT) Message-Id: <20150916.105936.2275139635170756984.davem@davemloft.net> To: David.Laight@ACULAB.COM Cc: haiyangz@microsoft.com, vkuznets@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kys@microsoft.com, jasowang@redhat.com Subject: Re: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V From: David Miller In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D1CB9800B@AcuExch.aculab.com> References: <1442418625-11805-1-git-send-email-vkuznets@redhat.com> <063D6719AE5E284EB5DD2968C1650D6D1CB9800B@AcuExch.aculab.com> X-Mailer: Mew version 6.7 on Emacs 24.5 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 16 Sep 2015 10:59:37 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: David Laight Date: Wed, 16 Sep 2015 16:25:03 +0000 > Am I right in thinking this is adding an extra 96 unused bytes to the front > of almost all skb just so that hyper-v can make its link level header > contiguous with whatever follows (IP header ?). > > Doesn't sound ideal. Agreed, this is rediculous, and the entire stack will incur this cost just because hyperv is enabled in the kernel config.