From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755031Ab3JaO0J (ORCPT ); Thu, 31 Oct 2013 10:26:09 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:57756 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754953Ab3JaO0F (ORCPT ); Thu, 31 Oct 2013 10:26:05 -0400 Message-ID: <1383229563.4857.71.camel@edumazet-glaptop.roam.corp.google.com> Subject: Re: [PATCH net-next V2 1/2] net: introduce skb_coalesce_rx_frag() From: Eric Dumazet To: Jason Wang Cc: davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, rusty@rustcorp.com.au, mst@redhat.com, mwdalton@google.com, virtualization@lists.linux-foundation.org, kmindg@gmail.com Date: Thu, 31 Oct 2013 07:26:03 -0700 In-Reply-To: <1383220027-12278-1-git-send-email-jasowang@redhat.com> References: <1383220027-12278-1-git-send-email-jasowang@redhat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2013-10-31 at 19:47 +0800, Jason Wang wrote: > Sometimes we need to coalesce the rx frags to avoid frag list. One example is > virtio-net driver which tries to use small frags for both MTU sized packet and > GSO packet. So this patch introduce skb_coalesce_rx_frag() to do this. > > Cc: Rusty Russell > Cc: Michael S. Tsirkin > Cc: Michael Dalton > Cc: Eric Dumazet > Acked-by: Michael S. Tsirkin > Signed-off-by: Jason Wang > --- > Changes from V1: > - remove the useless off parameter. > --- > include/linux/skbuff.h | 3 +++ > net/core/skbuff.c | 13 +++++++++++++ > 2 files changed, 16 insertions(+) > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 2c15497..fffaeaf 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -1372,6 +1372,9 @@ static inline void skb_fill_page_desc(struct sk_buff *skb, int i, > void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off, > int size, unsigned int truesize); > > +void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size, > + unsigned int truesize); > + > #define SKB_PAGE_ASSERT(skb) BUG_ON(skb_shinfo(skb)->nr_frags) > #define SKB_FRAG_ASSERT(skb) BUG_ON(skb_has_frag_list(skb)) > #define SKB_LINEAR_ASSERT(skb) BUG_ON(skb_is_nonlinear(skb)) > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 0ab32fa..87670e1 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -476,6 +476,19 @@ void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off, > } > EXPORT_SYMBOL(skb_add_rx_frag); > > +void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size, > + unsigned int truesize) > +{ > + skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; > + > + skb_frag_size_add(frag, size); > + skb->len += size; > + skb->data_len += size; > + skb->truesize += truesize; > + skb_frag_unref(skb, i); This unref is not logical, or should at least be __skb_frag_unref(frag); But I do think this is best done in the caller. In virtio_net this would be a : put_page(page); In tcp stack we do almost the same, but we take the reference on the page if we could not coalesce with prio frag, instead of doing a get and put in the other case. if (can_coalesce) { skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy); } else { get_page(page); skb_fill_page_desc(skb, i, page, offset, copy); } > +} > +EXPORT_SYMBOL(skb_coalesce_rx_frag); > + > static void skb_drop_list(struct sk_buff **listp) > { > kfree_skb_list(*listp);