From mboxrd@z Thu Jan 1 00:00:00 1970 From: Francois Romieu Subject: Re: [REGRESSION] r8169: jumbo fixes caused jumbo regressions! Date: Tue, 13 Nov 2012 23:35:12 +0100 Message-ID: <20121113223512.GA29342@electric-eye.fr.zoreil.com> References: <20121113170655.GA20291@tugrik.mns.mnsspb.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Realtek linux nic maintainers , Hayes Wang , "David S. Miller" , Greg Kroah-Hartman , netdev@vger.kernel.org To: Kirill Smelkov Return-path: Received: from violet.fr.zoreil.com ([92.243.8.30]:46402 "EHLO violet.fr.zoreil.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753683Ab2KMW6a (ORCPT ); Tue, 13 Nov 2012 17:58:30 -0500 Content-Disposition: inline In-Reply-To: <20121113170655.GA20291@tugrik.mns.mnsspb.ru> Sender: netdev-owner@vger.kernel.org List-ID: Kirill Smelkov : [...] > My test is to stream raw video from 8 PAL cameras to net - 4 for 720x576@25 and > 4 for 360x288@25 which for YUYV format occupies ~ 860 Mbps of bandwidth. The > program to transmit/receive video is here: http://repo.or.cz/w/rawv.git $ git clone http://repo.or.cz/w/rawv.git Cloning into 'rawv'... fatal: http://repo.or.cz/w/rawv.git/info/refs not valid: is this a git repository? [...] > (by the way, on atom system, without tx csum offload, half of cpu time > is spent only to calculate checksums...) :o( > Now I wonder, where that 6K limit came from and why they say it is now > not possible to use jumbos together with tx csum offload ? Here is an excerpt from a mail where Hayes explained the rules of engagement back in may 2011 (John Lumby and Chris Friesen were Cced then): ! The Max tx sizes for 8168 series are as following: ! ! 8168B is 4K bytes. ! 8168C and 8168CP are 6K bytes. ! 8168D and later are 9K bytes. ! ! Note that these sizes all include head size. That is, the mtu must less than ! these values. ! You have to enable Jumbo frame feature when the tx size is large, otherwise the ! packet would not be sent. Because the hw doesn't provide the threshold, the ! checking for MTU > 1500 is just for convenience for sw. ! ! The TSO couldn't work with some feature which need to disable hw checksum, such ! as Jumbo frame. The hw checksum have to be disabled in certain situations, so ! the TSO feature should be checked in these situations, too. > Is my testing enough to justify raising the limits and allowing tx offload ? I don't oppose knobs to go off-limits but I'll need some rather good reason before changing the manufacturer's suggested defaults. -- Ueimor