From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ido Schimmel Subject: Re: [PATCH net-next 4/4] ipv6: Add support for non-equal-cost multipath Date: Wed, 10 Jan 2018 13:47:38 +0200 Message-ID: <20180110114738.GA12249@splinter> References: <20180109144028.30133-1-idosch@mellanox.com> <20180109144028.30133-5-idosch@mellanox.com> <1dedd203-78ad-5290-fe27-9a8d376a991a@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ido Schimmel , netdev@vger.kernel.org, davem@davemloft.net, roopa@cumulusnetworks.com, nikolay@cumulusnetworks.com, pch@ordbogen.com, jkbs@redhat.com, yoshfuji@linux-ipv6.org, mlxsw@mellanox.com To: David Ahern Return-path: Received: from out3-smtp.messagingengine.com ([66.111.4.27]:39307 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751693AbeAJLrl (ORCPT ); Wed, 10 Jan 2018 06:47:41 -0500 Content-Disposition: inline In-Reply-To: <1dedd203-78ad-5290-fe27-9a8d376a991a@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Hi David, On Tue, Jan 09, 2018 at 08:48:37PM -0700, David Ahern wrote: > On 1/9/18 7:40 AM, Ido Schimmel wrote: > > The use of hash-threshold instead of modulo-N makes it trivial to add > > support for non-equal-cost multipath. > > > > Instead of dividing the multipath hash function's output space equally > > between the nexthops, each nexthop is assigned a region size which is > > proportional to its weight. > > > > Signed-off-by: Ido Schimmel > > --- > > include/net/ip6_fib.h | 1 + > > net/ipv6/route.c | 11 +++++++---- > > 2 files changed, 8 insertions(+), 4 deletions(-) > > > > diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h > > index 97cd05d87780..34ec321d6a03 100644 > > --- a/include/net/ip6_fib.h > > +++ b/include/net/ip6_fib.h > > @@ -171,6 +171,7 @@ struct rt6_info { > > u32 rt6i_metric; > > u32 rt6i_pmtu; > > /* more non-fragment space at head required */ > > + int rt6i_nh_weight; > > unsigned short rt6i_nfheader_len; > > u8 rt6i_protocol; > > u8 exception_bucket_flushed:1, > > Since dst is cacheline aligned there is a hole after rt6i_nh_flags. In > patch 1 you put rt6i_nh_upper_bound in that hole. Putting the weight > there too keeps those variables together as well as using the open space. Before patch 1 there's a hole of 4 bytes after rt6i_nh_flags which I use for rt6i_nh_upper_bound. If I put rt6i_nh_weight there as well, then I create a 60 bytes hole because the dst needs to be cached aligned. Since rt6i_nh_weight isn't used in fast-path, I just put it at the end.