netdev - Re: [PATCH net-next 3/4] ipv6: Use hash-threshold instead of modulo-N

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Message-ID: <397562a6-35ec-c5e4-b819-9931c1e5d86f@gmail.com>
Date:   Tue, 9 Jan 2018 20:54:00 -0700
From:   David Ahern <dsahern@...il.com>
To:     Ido Schimmel <idosch@...lanox.com>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, roopa@...ulusnetworks.com,
        nikolay@...ulusnetworks.com, pch@...bogen.com, jkbs@...hat.com,
        yoshfuji@...ux-ipv6.org, mlxsw@...lanox.com
Subject: Re: [PATCH net-next 3/4] ipv6: Use hash-threshold instead of modulo-N

On 1/9/18 7:40 AM, Ido Schimmel wrote:
> Now that each nexthop stores its region boundary in the multipath hash
> function's output space, we can use hash-threshold instead of modulo-N
> in multipath selection.
> 
> This reduces the number of checks we need to perform during lookup, as
> dead and linkdown nexthops are assigned a negative region boundary. In
> addition, in contrast to modulo-N, only flows near region boundaries are
> affected when a nexthop is added or removed.
> 
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> ---
>  net/ipv6/route.c | 36 +++++++++++++-----------------------
>  1 file changed, 13 insertions(+), 23 deletions(-)
> 

Did you consider adding the net->ipv4.sysctl_fib_multipath_use_neigh
check as well? ie., if set, verify neighbor is alive before picking that hop

Acked-by: David Ahern <dsahern@...il.com>