Date:   Fri, 29 Sep 2017 18:34:07 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     netdev@...r.kernel.org
Cc:     jakub.kicinski@...ronome.com,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>, mchan@...adcom.com,
        John Fastabend <john.fastabend@...il.com>,
        peter.waskiewicz.jr@...el.com,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>
Subject: [net-next V2 PATCH 0/5] New bpf cpumap type for XDP_REDIRECT

Introducing a new way to redirect XDP frames.  Notice how no driver
changes are necessary given the design of XDP_REDIRECT.

This redirect map type is called 'cpumap', as it allows redirection
XDP frames to remote CPUs.  The remote CPU will do the SKB allocation
and start the network stack invocation on that CPU.

This is a scalability and isolation mechanism, that allow separating
the early driver network XDP layer, from the rest of the netstack, and
assigning dedicated CPUs for this stage.  The sysadm control/configure
the RX-CPU to NIC-RX queue (as usual) via procfs smp_affinity and how
many queues are configured via ethtool --set-channels.  Benchmarks
show that a single CPU can handle approx 11Mpps.  Thus, only assigning
two NIC RX-queues (and two CPUs) is sufficient for handling 10Gbit/s
wirespeed smallest packet 14.88Mpps.  Reducing the number of queues
have the advantage that more packets being "bulk" available per hard
interrupt[1].

[1] https://www.netdevconf.org/2.1/papers/BusyPollingNextGen.pdf

Use-cases:

1. End-host based pre-filtering for DDoS mitigation.  This is fast
   enough to allow software to see and filter all packets wirespeed.
   Thus, no packets getting silently dropped by hardware.

2. Given NIC HW unevenly distributes packets across RX queue, this
   mechanism can be used for redistribution load across CPUs.  This
   usually happens when HW is unaware of a new protocol.  This
   resembles RPS (Receive Packet Steering), just faster, but with more
   responsibility placed on the BPF program for correct steering.

3. Auto-scaling or power saving via only activating the appropriate
   number of remote CPUs for handling the current load.  The cpumap
   tracepoints can function as a feedback loop for this purpose.

Patchset based on net-next at:
 commit 14a0d032f4ec ("Merge branch 'mlxsw-pass-gact'")

---

Jesper Dangaard Brouer (5):
      bpf: introduce new bpf cpu map type BPF_MAP_TYPE_CPUMAP
      bpf: XDP_REDIRECT enable use of cpumap
      bpf: cpumap xdp_buff to skb conversion and allocation
      bpf: cpumap add tracepoints
      samples/bpf: add cpumap sample program xdp_redirect_cpu


 include/linux/bpf.h                 |    7 
 include/linux/bpf_types.h           |    1 
 include/trace/events/xdp.h          |   80 ++++
 include/uapi/linux/bpf.h            |    1 
 kernel/bpf/Makefile                 |    1 
 kernel/bpf/cpumap.c                 |  686 +++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c                |    8 
 kernel/bpf/verifier.c               |    3 
 net/core/filter.c                   |   65 +++
 samples/bpf/Makefile                |    4 
 samples/bpf/xdp_redirect_cpu_kern.c |  640 +++++++++++++++++++++++++++++++++
 samples/bpf/xdp_redirect_cpu_user.c |  639 +++++++++++++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h      |    1 
 13 files changed, 2124 insertions(+), 12 deletions(-)
 create mode 100644 kernel/bpf/cpumap.c
 create mode 100644 samples/bpf/xdp_redirect_cpu_kern.c
 create mode 100644 samples/bpf/xdp_redirect_cpu_user.c

--

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