From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: Re: [PATCH net-next V1 1/2] net: Header length compution function Date: Mon, 28 Jul 2014 07:50:44 -0700 Message-ID: <53D66344.2050207@intel.com> References: <1406546881-21863-1-git-send-email-amirv@mellanox.com> <1406546881-21863-2-git-send-email-amirv@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , netdev@vger.kernel.org, Or Gerlitz , Yevgeny Petrilin , Ido Shamay , Eric Dumazet To: Amir Vadai , "David S. Miller" Return-path: Received: from mga02.intel.com ([134.134.136.20]:11695 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750915AbaG1OvV (ORCPT ); Mon, 28 Jul 2014 10:51:21 -0400 In-Reply-To: <1406546881-21863-2-git-send-email-amirv@mellanox.com> Sender: netdev-owner@vger.kernel.org List-ID: On 07/28/2014 04:28 AM, Amir Vadai wrote: > From: Eric Dumazet > > This commit is based on Eric Dumazet suggestion. > Use flow dissector to calculate header length. > Tested the following with a mlx4, and it indeed speeds up GRE traffic, > as GRO packets can now contain 17 MSS instead of 8. > (Pulling payload means GRO had to use 2 'frags' per MSS) > > Signed-off-by: Eric Dumazet > Signed-off-by: Amir Vadai > --- > include/linux/skbuff.h | 1 + > net/core/flow_dissector.c | 24 ++++++++++++++++++++++++ > 2 files changed, 25 insertions(+) > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index b613557..1f9af4d 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -3133,6 +3133,7 @@ bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off); > int skb_checksum_setup(struct sk_buff *skb, bool recalculate); > > u32 __skb_get_poff(const struct sk_buff *skb); > +u32 eth_frame_headlen(void *data, unsigned int len); > > /** > * skb_head_is_locked - Determine if the skb->head is locked down > diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c > index 5f362c1..c3afd27 100644 > --- a/net/core/flow_dissector.c > +++ b/net/core/flow_dissector.c > @@ -343,6 +343,30 @@ u32 __skb_get_poff(const struct sk_buff *skb) > return poff; > } > > + > +/* Helper to find length of headers in an ethernet frame. > + * This can help drivers to pull exact amount of bytes into > + * skb->head to get optimal GRO performance. > + * TODO: Could also return rxhash while we do a complete flow dissection. > + */ > +u32 eth_frame_headlen(void *data, unsigned int len) > +{ > + const struct ethhdr *eth = data; > + struct sk_buff skb; > + > + if (unlikely(len < ETH_HLEN)) > + return len; > + > + skb.protocol = eth->h_proto; > + skb.head = data + ETH_HLEN; > + skb.data = skb.head; > + skb_reset_network_header(&skb); > + skb.len = len - ETH_HLEN; > + skb.data_len = 0; > + return __skb_get_poff(&skb) + ETH_HLEN; > +} I'm still not a big fan of allocating an sk_buff on the stack. Seems like it isn't maintainable and really opens things up to possible issues if someone ever extends the __skb_get_poff call. But I'm not going to force the issue since for now this isn't impacting igb or ixgbe. Thanks, Alex