From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH v4 net-next 01/15] nfp: correct RX buffer length calculation Date: Tue, 05 Apr 2016 11:39:17 -0400 (EDT) Message-ID: <20160405.113917.846241936652070162.davem@davemloft.net> References: <1459544811-24879-1-git-send-email-jakub.kicinski@netronome.com> <1459544811-24879-2-git-send-email-jakub.kicinski@netronome.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: jakub.kicinski@netronome.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:59026 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932823AbcDEPj2 (ORCPT ); Tue, 5 Apr 2016 11:39:28 -0400 In-Reply-To: <1459544811-24879-2-git-send-email-jakub.kicinski@netronome.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Jakub Kicinski Date: Fri, 1 Apr 2016 22:06:37 +0100 > When calculating the RX buffer length we need to account for > up to 2 VLAN tags and up to 8 MPLS labels. Rounding up to 1k > is an relic of a distant past and can be removed. While at > it also remove trivial print statement. > > Signed-off-by: Jakub Kicinski I disagree with the MPLS aspect of this change. VLAN is special, in that when the hardware supports VLAN properly, the VLAN header doesn't eat into the MTU and is sort of "transparent". But MPLS doesn't work that way. MPLS is in the main frame and takes up MTU space. Therefore I see no reason to increase the buffer length by 8 * MPLS which is just a rediculous amount of wasted space. I'm not applying this without at least some more explanations about why exactly you need to account for these values in the commit message.