Date:   Fri, 10 Aug 2018 16:24:55 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Toshiaki Makita <makita.toshiaki@....ntt.co.jp>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     netdev@...r.kernel.org, Jesper Dangaard Brouer <brouer@...hat.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH v8 bpf-next 00/10] veth: Driver XDP

On 08/03/2018 09:58 AM, Toshiaki Makita wrote:
> This patch set introduces driver XDP for veth.
> Basically this is used in conjunction with redirect action of another XDP
> program.
> 
>   NIC -----------> veth===veth
>  (XDP) (redirect)        (XDP)
> 
> In this case xdp_frame can be forwarded to the peer veth without
> modification, so we can expect far better performance than generic XDP.
> 
> 
> Envisioned use-cases
> --------------------
> 
> * Container managed XDP program
> Container host redirects frames to containers by XDP redirect action, and
> privileged containers can deploy their own XDP programs.
> 
> * XDP program cascading
> Two or more XDP programs can be called for each packet by redirecting
> xdp frames to veth.
> 
> * Internal interface for an XDP bridge
> When using XDP redirection to create a virtual bridge, veth can be used
> to create an internal interface for the bridge.
> 
> 
> Implementation
> --------------
> 
> This changeset is making use of NAPI to implement ndo_xdp_xmit and
> XDP_TX/REDIRECT. This is mainly because XDP heavily relies on NAPI
> context.
>  - patch 1: Export a function needed for veth XDP.
>  - patch 2-3: Basic implementation of veth XDP.
>  - patch 4-6: Add ndo_xdp_xmit.
>  - patch 7-9: Add XDP_TX and XDP_REDIRECT.
>  - patch 10: Performance optimization for multi-queue env.
> 
> 
> Tests and performance numbers
> -----------------------------
> 
> Tested with a simple XDP program which only redirects packets between
> NIC and veth. I used i40e 25G NIC (XXV710) for the physical NIC. The
> server has 20 of Xeon Silver 2.20 GHz cores.
> 
>   pktgen --(wire)--> XXV710 (i40e) <--(XDP redirect)--> veth===veth (XDP)
> 
> The rightmost veth loads XDP progs and just does DROP or TX. The number
> of packets is measured in the XDP progs. The leftmost pktgen sends
> packets at 37.1 Mpps (almost 25G wire speed).
> 
> veth XDP action    Flows    Mpps
> ================================
> DROP                   1    10.6
> DROP                   2    21.2
> DROP                 100    36.0
> TX                     1     5.0
> TX                     2    10.0
> TX                   100    31.0
> 
> I also measured netperf TCP_STREAM but was not so great performance due
> to lack of tx/rx checksum offload and TSO, etc.
> 
>   netperf <--(wire)--> XXV710 (i40e) <--(XDP redirect)--> veth===veth (XDP PASS)
> 
> Direction         Flows   Gbps
> ==============================
> external->veth        1   20.8
> external->veth        2   23.5
> external->veth      100   23.6
> veth->external        1    9.0
> veth->external        2   17.8
> veth->external      100   22.9
> 
> Also tested doing ifup/down or load/unload a XDP program repeatedly
> during processing XDP packets in order to check if enabling/disabling
> NAPI is working as expected, and found no problems.
> 
> v8:
> - Don't use xdp_frame pointer address to calculate skb->head, headroom,
>   and xdp_buff.data_hard_start.
> 
> v7:
> - Introduce xdp_scrub_frame() to clear kernel pointers in xdp_frame and
>   use it instead of memset().
> 
> v6:
> - Check skb->len only if reallocation is needed.
> - Add __GFP_NOWARN to alloc_page() since it can be triggered by external
>   events.
> - Fix sparse warning around EXPORT_SYMBOL.
> 
> v5:
> - Fix broken SOBs.
> 
> v4:
> - Don't adjust MTU automatically.
> - Skip peer IFF_UP check on .ndo_xdp_xmit() because it is unnecessary.
>   Add comments to explain that.
> - Use redirect_info instead of xdp_mem_info for storing no_direct flag
>   to avoid per packet copy cost.
> 
> v3:
> - Drop skb bulk xmit patch since it makes little performance
>   difference. The hotspot in TCP skb xmit at this point is checksum
>   computation in skb_segment and packet copy on XDP_REDIRECT due to
>   cloned/nonlinear skb.
> - Fix race on closing device.
> - Add extack messages in ndo_bpf.
> 
> v2:
> - Squash NAPI patch with "Add driver XDP" patch.
> - Remove conversion from xdp_frame to skb when NAPI is not enabled.
> - Introduce per-queue XDP ring (patch 8).
> - Introduce bulk skb xmit when XDP is enabled on the peer (patch 9).
> 
> Signed-off-by: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
> 
> Toshiaki Makita (10):
>   net: Export skb_headers_offset_update
>   veth: Add driver XDP
>   veth: Avoid drops by oversized packets when XDP is enabled
>   xdp: Helper function to clear kernel pointers in xdp_frame
>   veth: Handle xdp_frames in xdp napi ring
>   veth: Add ndo_xdp_xmit
>   bpf: Make redirect_info accessible from modules
>   xdp: Helpers for disabling napi_direct of xdp_return_frame
>   veth: Add XDP TX and REDIRECT
>   veth: Support per queue XDP ring
> 
>  drivers/net/veth.c     | 750 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  include/linux/filter.h |  35 +++
>  include/linux/skbuff.h |   1 +
>  include/net/xdp.h      |   7 +
>  net/core/filter.c      |  29 +-
>  net/core/skbuff.c      |   3 +-
>  net/core/xdp.c         |   6 +-
>  7 files changed, 801 insertions(+), 30 deletions(-)
> 

Applied to bpf-next, thanks Toshiaki!

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