netdev - Re: [bpf-next PATCH 2/2] samples/bpf: xdp_redirect

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Date:   Thu, 9 Aug 2018 22:15:22 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org
Cc:     Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        jhsiao@...hat.com
Subject: Re: [bpf-next PATCH 2/2] samples/bpf: xdp_redirect_cpu load balance
 like Suricata

On 08/09/2018 03:26 PM, Jesper Dangaard Brouer wrote:
> This implement XDP CPU redirection load-balancing across available
> CPUs, based on the hashing IP-pairs + L4-protocol.  This equivalent to
> xdp-cpu-redirect feature in Suricata, which is inspired by the
> Suricata 'ippair' hashing code.
> 
> An important property is that the hashing is flow symmetric, meaning
> that if the source and destination gets swapped then the selected CPU
> will remain the same.  This is helps locality by placing both directions
> of a flows on the same CPU, in a forwarding/routing scenario.
> 
> The hashing INITVAL (15485863 the 10^6th prime number) was fairly
> arbitrary choosen, but experiments with kernel tree pktgen scripts
> (pktgen_sample04_many_flows.sh +pktgen_sample05_flow_per_thread.sh)
> showed this improved the distribution.
> 
> This patch also change the default loaded XDP program to be this
> load-balancer.  As based on different user feedback, this seems to be
> the expected behavior of the sample xdp_redirect_cpu.
> 
> Link: https://github.com/OISF/suricata/commit/796ec08dd7a63
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> ---
>  samples/bpf/xdp_redirect_cpu_kern.c |  103 +++++++++++++++++++++++++++++++++++
>  samples/bpf/xdp_redirect_cpu_user.c |    4 +
>  2 files changed, 105 insertions(+), 2 deletions(-)
> 
> diff --git a/samples/bpf/xdp_redirect_cpu_kern.c b/samples/bpf/xdp_redirect_cpu_kern.c
> index 0cc3d71057f0..a306d1c75622 100644
> --- a/samples/bpf/xdp_redirect_cpu_kern.c
> +++ b/samples/bpf/xdp_redirect_cpu_kern.c
> @@ -13,6 +13,7 @@
>  
>  #include <uapi/linux/bpf.h>
>  #include "bpf_helpers.h"
> +#include "hash_func01.h"
>  
>  #define MAX_CPUS 64 /* WARNING - sync with _user.c */

Hmm, this doesn't apply cleanly. I have the following in bpf-next:

#define MAX_CPUS 12 /* WARNING - sync with _user.c */

https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/samples/bpf/xdp_redirect_cpu_kern.c#n17

Rebase issue? Please respin, thanks.