From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: Add NAPI support to ll_temac driver Date: Tue, 19 Apr 2011 14:14:58 +0100 Message-ID: <1303218898.3464.59.camel@localhost> References: <4DAD5753.4040108@monstr.eu> <1303209787.3480.9.camel@edumazet-laptop> <1303215925.3464.54.camel@localhost> <4DAD84B1.9020405@monstr.eu> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , netdev@vger.kernel.org To: monstr@monstr.eu Return-path: Received: from mail.solarflare.com ([216.237.3.220]:57483 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752497Ab1DSNPC (ORCPT ); Tue, 19 Apr 2011 09:15:02 -0400 In-Reply-To: <4DAD84B1.9020405@monstr.eu> Sender: netdev-owner@vger.kernel.org List-ID: 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. Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.