netdev - Re: [PATCH bpf-next 0/8] Simplify xdp_do_redirect_map()/xdp_do_flush

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Date:   Wed, 18 Dec 2019 13:32:05 +0100
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        bpf <bpf@...r.kernel.org>, David Miller <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Maciej Fijalkowski <maciejromanfijalkowski@...il.com>
Subject: Re: [PATCH bpf-next 0/8] Simplify xdp_do_redirect_map()/xdp_do_flush_map()
 and XDP maps

On Wed, 18 Dec 2019 at 13:18, Björn Töpel <bjorn.topel@...il.com> wrote:
>
> On Wed, 18 Dec 2019 at 13:04, Jesper Dangaard Brouer <brouer@...hat.com> wrote:
> >
> > On Wed, 18 Dec 2019 12:39:53 +0100
> > Björn Töpel <bjorn.topel@...il.com> wrote:
> >
> > > On Wed, 18 Dec 2019 at 12:11, Jesper Dangaard Brouer <brouer@...hat.com> wrote:
> > > >
> > > > On Wed, 18 Dec 2019 11:53:52 +0100
> > > > Björn Töpel <bjorn.topel@...il.com> wrote:
> > > >
> > > > >   $ sudo ./xdp_redirect_cpu --dev enp134s0f0 --cpu 22 xdp_cpu_map0
> > > > >
> > > > >   Running XDP/eBPF prog_name:xdp_cpu_map5_lb_hash_ip_pairs
> > > > >   XDP-cpumap      CPU:to  pps            drop-pps    extra-info
> > > > >   XDP-RX          20      7723038        0           0
> > > > >   XDP-RX          total   7723038        0
> > > > >   cpumap_kthread  total   0              0           0
> > > > >   redirect_err    total   0              0
> > > > >   xdp_exception   total   0              0
> > > >
> > > > Hmm... I'm missing some counters on the kthread side.
> > > >
> > >
> > > Oh? Any ideas why? I just ran the upstream sample straight off.
> >
> > Looks like it happened in commit: bbaf6029c49c ("samples/bpf: Convert
> > XDP samples to libbpf usage") (Cc Maciej).
> >
> > The old bpf_load.c will auto attach the tracepoints... for and libbpf
> > you have to be explicit about it.
> >
> > Can I ask you to also run a test with --stress-mode for
> > ./xdp_redirect_cpu, to flush out any potential RCU race-conditions
> > (don't provide output, this is just a robustness test).
> >
>
> Sure! Other than that, does the command line above make sense? I'm
> blasting UDP packets to core 20, and the idea was to re-route them to
> 22.
>

No, crash with --stress-mode/-x. (Still no tracepoint output.) And
bpf_redirect_map() is executed and the cpu_map thread is running. :-P