From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Simek Subject: Re: net: more accurate skb truesize - regression on Microblaze Date: Tue, 10 Apr 2012 13:38:33 +0200 Message-ID: <4F841BB9.2030209@monstr.eu> References: <4F83EB0E.4020104@monstr.eu> <1334046444.3126.12.camel@edumazet-glaptop> <1334046746.3126.13.camel@edumazet-glaptop> <4F83F166.4010208@monstr.eu> <1334057529.3126.90.camel@edumazet-glaptop> Reply-To: monstr@monstr.eu Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, John Williams , David Miller To: Eric Dumazet Return-path: Received: from mail-ee0-f46.google.com ([74.125.83.46]:57712 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751398Ab2DJLii (ORCPT ); Tue, 10 Apr 2012 07:38:38 -0400 Received: by eekc41 with SMTP id c41so1295609eek.19 for ; Tue, 10 Apr 2012 04:38:37 -0700 (PDT) In-Reply-To: <1334057529.3126.90.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On 04/10/2012 01:32 PM, Eric Dumazet wrote: > On Tue, 2012-04-10 at 10:37 +0200, Michal Simek wrote: >> On 04/10/2012 10:32 AM, Eric Dumazet wrote: >>> On Tue, 2012-04-10 at 10:27 +0200, Eric Dumazet wrote: >>> >>>> BTW, some NIC drivers are known to provide fat skb in their rx path, and >>>> need to be fixed as well. (Some others just lie about skb->truesize to >>>> avoid the tcp slowdown, see my previous iwlwifi patch) >>>> >>>> >>> >>> What is the driver you currently use on your platform ? >> >> Using Xilinx ll_temac(in mainline) and axi_emac. >> > > ll_temac allocates XTE_MAX_JUMBO_FRAME_SIZE frames, even for MTU=1500 ? yes. > > Trying to allocate smaller packets would definitely help your tcp > receiver performance and overall reliability (order-0 allocations > instead of order-2) There is long history for ll_temac and axi emac drivers. and if you compare them they are very similar with similar bugs. In our distribution we are using older ll_temac driver where this is fixed. Performance is much higher if you allocate buffers for actual mtu. Thanks, Michal P.S.: Our plan is to start to use mainline drivers and fixing them to get the same performance as we have with old one. It is one my todo list. -- Michal Simek, Ing. (M.Eng) w: www.monstr.eu p: +42-0-721842854 Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/ Microblaze U-BOOT custodian