From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Simek Subject: Re: Add NAPI support to ll_temac driver Date: Tue, 19 Apr 2011 15:18:06 +0200 Message-ID: <4DAD8B8E.1010008@monstr.eu> References: <4DAD5753.4040108@monstr.eu> <1303209787.3480.9.camel@edumazet-laptop> <1303215925.3464.54.camel@localhost> <4DAD84B1.9020405@monstr.eu> <1303218898.3464.59.camel@localhost> Reply-To: monstr@monstr.eu Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , netdev@vger.kernel.org To: Ben Hutchings Return-path: Received: from mail-bw0-f46.google.com ([209.85.214.46]:53143 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755034Ab1DSNSY (ORCPT ); Tue, 19 Apr 2011 09:18:24 -0400 Received: by bwz15 with SMTP id 15so4516618bwz.19 for ; Tue, 19 Apr 2011 06:18:23 -0700 (PDT) In-Reply-To: <1303218898.3464.59.camel@localhost> Sender: netdev-owner@vger.kernel.org List-ID: Ben Hutchings wrote: > On Tue, 2011-04-19 at 14:48 +0200, Michal Simek wrote: >> Ben Hutchings wrote: >>> On Tue, 2011-04-19 at 12:43 +0200, Eric Dumazet wrote: >>> [...] >>>> One possible way to get better performance is to change driver to >>>> allocate skbs only right before calling netif_rx(), so that you dont >>>> have to access cold sk_buff data twice (once when allocating skb and put >>>> it in ring buffer, a second time when receiving frame) >>>> >>>> drivers/net/niu.c is a good example for this (NAPI + netdev_alloc_skb() >>>> just in time + pull in skbhead only first cache line of packet) >>> [...] >>> >>> If the hardware can do RX checksumming (it's not clear) then the driver >>> should pass the paged buffers into GRO and that will take care of skb >>> allocation as necessary. >> Hardware supports RX and TX partial checksumming. I can enable it. The driver >> has also this option and from my tests there is of course some performance >> improvemetn. >> >> Just for sure - here are links on documentation. >> http://www.xilinx.com/support/documentation/ip_documentation/xps_ll_temac.pdf >> or >> http://www.xilinx.com/support/documentation/ip_documentation/axi_ethernet/v2_01_a/ds759_axi_ethernet.pdf > > I'm not going to read those. Just providing brief advice. > >> About SKB allocation. I fixed our non mainline driver to allocate skb based on >> current mtu size. Mainline driver allocate max mtu (9k). This has also impact on >> performance because Microblaze works with smaller SKBs. >> >> Can you please be more specific about passing the paged buffers into GRO? >> Or point me to any documentation or code which can help me to understand what >> that means. > > You would use napi_get_frags() to get a new or recycled skb, fill in > skb->frags, then call napi_gro_frags() to pass it into GRO. The benet, > cxgb3 and sfc drivers do this. ok. Will look. Thanks, Michal -- 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