Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751717AbZIOJPP (ORCPT ); Tue, 15 Sep 2009 05:15:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750882AbZIOJPN (ORCPT ); Tue, 15 Sep 2009 05:15:13 -0400 Received: from mga02.intel.com ([134.134.136.20]:20263 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750785AbZIOJPM (ORCPT ); Tue, 15 Sep 2009 05:15:12 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.44,388,1249282800"; d="scan'208";a="550676049" Subject: Re: alloc skb based on a given data buffer From: Zhu Yi To: David Miller Cc: "mel@csn.ul.ie" , "Chatre, Reinette" , "elendil@planet.nl" , "Larry.Finger@lwfinger.net" , "linville@tuxdriver.com" , "penberg@cs.helsinki.fi" , "linux-kernel@vger.kernel.org" , "linux-wireless@vger.kernel.org" , "ipw3945-devel@lists.sourceforge.net" , "akpm@linux-foundation.org" , "cl@linux-foundation.org" , "Krauss, Assaf" , "johannes@sipsolutions.net" , "Abbas, Mohamed" , "netdev@vger.kernel.org" In-Reply-To: <20090915.020903.93643290.davem@davemloft.net> References: <1253003420.7549.51.camel@debian> <20090915.013321.07006714.davem@davemloft.net> <1253005050.7549.58.camel@debian> <20090915.020903.93643290.davem@davemloft.net> Content-Type: text/plain Date: Tue, 15 Sep 2009 17:15:11 +0800 Message-Id: <1253006111.7549.61.camel@debian> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1560 Lines: 50 On Tue, 2009-09-15 at 17:09 +0800, David Miller wrote: > From: Zhu Yi > Date: Tue, 15 Sep 2009 16:57:29 +0800 > > > Thanks. So we can put the 8K buffer into 2 skb_shinfo()->frags[] slots > > and set nr_frags to 2, right? Is this supported allover the network code > > already? At a first glance, I didn't find any frags handling in mac80211 > > stack. > > You have to pre-pull the link level protocol headers into the > linear area, but that's it. > > Again, see niu.c for details, it does: > > static void niu_rx_skb_append(struct sk_buff *skb, struct page *page, > u32 offset, u32 size) > { > int i = skb_shinfo(skb)->nr_frags; > skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; > > frag->page = page; > frag->page_offset = offset; > frag->size = size; > > skb->len += size; > skb->data_len += size; > skb->truesize += size; > > skb_shinfo(skb)->nr_frags = i + 1; > } > > to add pages to SKBs and then at the end it goes: > > skb_reserve(skb, NET_IP_ALIGN); > __pskb_pull_tail(skb, min(len, NIU_RXPULL_MAX)); > > Right before giving the SKB to the networking stack. NIU_RXPULL_MAX > should be a value that will be large enough to cover the largest > possible link level header. I see. Thanks for this info. I'll try implementing the same for iwlagn. Thanks, -yi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/