linux-kernel - Re: [PATCH] bpf: validate bpf_func when BPF

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Message-ID: <87impzt4pu.fsf@toke.dk>
Date:   Wed, 11 Sep 2019 13:09:01 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Björn Töpel <bjorn.topel@...el.com>,
        Yonghong Song <yhs@...com>,
        Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kees Cook <keescook@...omium.org>, Martin Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        "netdev\@vger.kernel.org" <netdev@...r.kernel.org>,
        "bpf\@vger.kernel.org" <bpf@...r.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH] bpf: validate bpf_func when BPF_JIT is enabled

Björn Töpel <bjorn.topel@...el.com> writes:

> On 2019-09-11 09:42, Yonghong Song wrote:
>> I am not an expert in XDP testing. Toke, Björn, could you give some
>> suggestions what to test for XDP performance here?
>
> I ran the "xdp_rxq_info" sample with and without Sami's patch:

Thanks for doing this!

> $ sudo ./xdp_rxq_info --dev enp134s0f0 --action XDP_DROP
>
> Before:
>
> Running XDP on dev:enp134s0f0 (ifindex:6) action:XDP_DROP options:no_touch
> XDP stats       CPU     pps         issue-pps
> XDP-RX CPU      20      23923874    0
> XDP-RX CPU      total   23923874
>
> RXQ stats       RXQ:CPU pps         issue-pps
> rx_queue_index   20:20  23923878    0
> rx_queue_index   20:sum 23923878
>
> After Sami's patch:
>
> Running XDP on dev:enp134s0f0 (ifindex:6) action:XDP_DROP options:no_touch
> XDP stats       CPU     pps         issue-pps
> XDP-RX CPU      20      22998700    0
> XDP-RX CPU      total   22998700
>
> RXQ stats       RXQ:CPU pps         issue-pps
> rx_queue_index   20:20  22998705    0
> rx_queue_index   20:sum 22998705
>
>
> So, roughly ~4% for this somewhat naive scenario.

Or (1/22998700 - 1/23923874) * 10**9 == 1.7 nanoseconds of overhead.

I guess that is not *too* bad; but it's still chipping away at
performance; anything we could do to lower the overhead?

-Toke