From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Cc: Lorenzo Bianconi <lorenzo@kernel.org>,
BPF-dev-list <bpf@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Song Liu <song@kernel.org>,
Toke Hoiland Jorgensen <toke@redhat.com>,
brouer@redhat.com
Subject: Re: [PATCH v3 bpf-next] cpumap: bulk skb using netif_receive_skb_list
Date: Thu, 22 Apr 2021 14:30:57 +0200 [thread overview]
Message-ID: <20210422143057.223aa339@carbon> (raw)
In-Reply-To: <CAJ0CqmVozWi5uCnzWCpkc5kccnEJWRNbLMb-5YmWe7te9E_Odg@mail.gmail.com>
On Thu, 22 Apr 2021 12:59:31 +0200
Lorenzo Bianconi <lorenzo.bianconi@redhat.com> wrote:
> >
> > [...]
> > > > + TP_ARGS(map_id, processed, sched, xdp_stats),
> > > >
> > > > TP_STRUCT__entry(
> > > > __field(int, map_id)
> > > > __field(u32, act)
> > > > __field(int, cpu)
> > > > - __field(unsigned int, drops)
> > > > __field(unsigned int, processed)
> > >
> > > So, struct member @processed will takeover the room for @drops.
> > >
> > > Can you please test how an old xdp_monitor program will react to this?
> > > Will it fail, or extract and show wrong values?
> >
> > Ack, right. I think we should keep the struct layout in order to maintain
> > back-compatibility. I will fix it in v4.
> >
> > >
> > > The xdp_mointor tool is in several external git repos:
> > >
> > > https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/samples/bpf/xdp_monitor_kern.c
> > > https://github.com/xdp-project/xdp-tutorial/tree/master/tracing02-xdp-monitor
>
> Running an old version of xdp_monitor with a patched kernel, I
> verified the xdp sample does not crash but it reports wrong values
> (e.g. pps are reported as drops for tracepoint disagliment).
> I think we have two possibilities here:
> - assuming tracepoints are not a stable ABI, we can just fix xdp
> samples available in the kernel tree and provide a patch for
> xdp-project
>
> - keep current tracepoint layout and just rename current drop variable
> in bpf/cpumap.c in something like skb_alloc_drop.
I like this one the most, rename to skb_alloc_drop, but keep layout.
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
prev parent reply other threads:[~2021-04-22 12:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 14:05 [PATCH v3 bpf-next] cpumap: bulk skb using netif_receive_skb_list Lorenzo Bianconi
2021-04-20 16:54 ` Jesper Dangaard Brouer
2021-04-20 17:09 ` Lorenzo Bianconi
2021-04-22 10:59 ` Lorenzo Bianconi
2021-04-22 12:30 ` Jesper Dangaard Brouer [this message]
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