From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Hangbin Liu <liuhangbin@gmail.com>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
"Toke Høiland-Jørgensen" <toke@redhat.com>,
"Jiri Benc" <jbenc@redhat.com>,
"Eelco Chaudron" <echaudro@redhat.com>,
ast@kernel.org, "Daniel Borkmann" <daniel@iogearbox.net>,
"Lorenzo Bianconi" <lorenzo.bianconi@redhat.com>,
"David Ahern" <dsahern@gmail.com>,
"Andrii Nakryiko" <andrii.nakryiko@gmail.com>,
"Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
"John Fastabend" <john.fastabend@gmail.com>,
"Maciej Fijalkowski" <maciej.fijalkowski@intel.com>,
"Björn Töpel" <bjorn.topel@gmail.com>,
"Martin KaFai Lau" <kafai@fb.com>,
brouer@redhat.com
Subject: Re: [PATCH RESEND v11 1/4] bpf: run devmap xdp_prog on flush instead of bulk enqueue
Date: Fri, 14 May 2021 08:49:56 +0200 [thread overview]
Message-ID: <20210514084956.2e41f3dd@carbon> (raw)
In-Reply-To: <20210513070447.1878448-2-liuhangbin@gmail.com>
On Thu, 13 May 2021 15:04:44 +0800
Hangbin Liu <liuhangbin@gmail.com> wrote:
> From: Jesper Dangaard Brouer <brouer@redhat.com>
>
> This changes the devmap XDP program support to run the program when the
> bulk queue is flushed instead of before the frame is enqueued. This has
> a couple of benefits:
>
> - It "sorts" the packets by destination devmap entry, and then runs the
> same BPF program on all the packets in sequence. This ensures that we
> keep the XDP program and destination device properties hot in I-cache.
>
> - It makes the multicast implementation simpler because it can just
> enqueue packets using bq_enqueue() without having to deal with the
> devmap program at all.
>
> The drawback is that if the devmap program drops the packet, the enqueue
> step is redundant. However, arguably this is mostly visible in a
> micro-benchmark, and with more mixed traffic the I-cache benefit should
> win out. The performance impact of just this patch is as follows:
>
> Using 2 10Gb i40e NIC, redirecting one to another, or into a veth interface,
> which do XDP_DROP on veth peer. With xdp_redirect_map in sample/bpf, send
> pkts via pktgen cmd:
> ./pktgen_sample03_burst_single_flow.sh -i eno1 -d $dst_ip -m $dst_mac -t 10 -s 64
>
> There are about +/- 0.1M deviation for native testing, the performance
> improved for the base-case, but some drop back with xdp devmap prog attached.
>
> Version | Test | Generic | Native | Native + 2nd xdp_prog
> 5.12 rc4 | xdp_redirect_map i40e->i40e | 1.9M | 9.6M | 8.4M
> 5.12 rc4 | xdp_redirect_map i40e->veth | 1.7M | 11.7M | 9.8M
> 5.12 rc4 + patch | xdp_redirect_map i40e->i40e | 1.9M | 9.8M | 8.0M
> 5.12 rc4 + patch | xdp_redirect_map i40e->veth | 1.7M | 12.0M | 9.4M
>
> When bq_xmit_all() is called from bq_enqueue(), another packet will
> always be enqueued immediately after, so clearing dev_rx, xdp_prog and
> flush_node in bq_xmit_all() is redundant. Move the clear to __dev_flush(),
> and only check them once in bq_enqueue() since they are all modified
> together.
>
> This change also has the side effect of extending the lifetime of the
> RCU-protected xdp_prog that lives inside the devmap entries: Instead of
> just living for the duration of the XDP program invocation, the
> reference now lives all the way until the bq is flushed. This is safe
> because the bq flush happens at the end of the NAPI poll loop, so
> everything happens between a local_bh_disable()/local_bh_enable() pair.
> However, this is by no means obvious from looking at the call sites; in
> particular, some drivers have an additional rcu_read_lock() around only
> the XDP program invocation, which only confuses matters further.
> Cleaning this up will be done in a separate patch series.
>
> Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
For the sake of good order
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2021-05-14 6:50 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-13 7:04 [PATCH RESEND v11 0/4] xdp: extend xdp_redirect_map with broadcast support Hangbin Liu
2021-05-13 7:04 ` [PATCH RESEND v11 1/4] bpf: run devmap xdp_prog on flush instead of bulk enqueue Hangbin Liu
2021-05-13 22:23 ` John Fastabend
2021-05-14 6:49 ` Jesper Dangaard Brouer [this message]
2021-05-13 7:04 ` [PATCH RESEND v11 2/4] xdp: extend xdp_redirect_map with broadcast support Hangbin Liu
2021-05-13 20:01 ` John Fastabend
2021-05-14 6:21 ` Jesper Dangaard Brouer
2021-05-18 20:36 ` Daniel Borkmann
2021-05-13 7:04 ` [PATCH RESEND v11 3/4] sample/bpf: add xdp_redirect_map_multi for redirect_map broadcast test Hangbin Liu
2021-05-13 7:04 ` [PATCH RESEND v11 4/4] selftests/bpf: add xdp_redirect_multi test Hangbin Liu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210514084956.2e41f3dd@carbon \
--to=brouer@redhat.com \
--cc=alexei.starovoitov@gmail.com \
--cc=andrii.nakryiko@gmail.com \
--cc=ast@kernel.org \
--cc=bjorn.topel@gmail.com \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=dsahern@gmail.com \
--cc=echaudro@redhat.com \
--cc=jbenc@redhat.com \
--cc=john.fastabend@gmail.com \
--cc=kafai@fb.com \
--cc=liuhangbin@gmail.com \
--cc=lorenzo.bianconi@redhat.com \
--cc=maciej.fijalkowski@intel.com \
--cc=netdev@vger.kernel.org \
--cc=toke@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).