From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH -next] net: preserve geometry of fragment sizes when forwarding Date: Mon, 18 May 2015 16:55:50 -0400 (EDT) Message-ID: <20150518.165550.359134808190719687.davem@davemloft.net> References: <20150518200637.GB20709@breakpoint.cc> <20150518.162854.1116793790405432801.davem@davemloft.net> <20150518204049.GC20709@breakpoint.cc> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, hannes@stressinduktion.org, edumazet@google.com, herbert@gondor.apana.org.au To: fw@strlen.de Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:60255 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750940AbbERUz5 (ORCPT ); Mon, 18 May 2015 16:55:57 -0400 In-Reply-To: <20150518204049.GC20709@breakpoint.cc> Sender: netdev-owner@vger.kernel.org List-ID: From: Florian Westphal Date: Mon, 18 May 2015 22:40:49 +0200 > But, to the best of my understanding, what you ask will push a lot of > non-trivial code into the kernel for no functional gain over > what has been proposed. The functional gain is that we stop linearizing the packet, which involves memory allocation and copying the entire packet. I am very confident that the performance gains would be non-trivial and quite measurable. You'd also be able to trivially respect the geometry of the original incoming packet stream. Every objection has been of the form "this special case" (this time SIP) is not easy. If I were doing this, I would implement something that handles the normal cases properly. And then take it from there. If you try to imagine the totality of it and all the edge cases and details from the beginning, yes it will look impossible.