netdev - Re: [PATCH bpf-next v2 0/4] introduce bpf

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Date:   Sat, 11 Dec 2021 17:50:37 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Hou Tao <houtao1@...wei.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>, Yonghong Song <yhs@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2 0/4] introduce bpf_strncmp() helper

On Fri, Dec 10, 2021 at 6:01 AM Hou Tao <houtao1@...wei.com> wrote:
>
> Hi,
>
> The motivation for introducing bpf_strncmp() helper comes from
> two aspects:
>
> (1) clang doesn't always replace strncmp() automatically
> In tracing program, sometimes we need to using a home-made
> strncmp() to check whether or not the file name is expected.
>
> (2) the performance of home-made strncmp is not so good
> As shown in the benchmark in patch #4, the performance of
> bpf_strncmp() helper is 18% or 33% better than home-made strncmp()
> under x86-64 or arm64 when the compared string length is 64. When
> the string length grows to 4095, the performance win will be
> 179% or 600% under x86-64 or arm64.
>
> Any comments are welcome.
> Regards,
> Tao
>
> Change Log:
> v2:
>  * rebased on bpf-next
>  * drop patch "selftests/bpf: factor out common helpers for benchmarks"
>    (suggested by Andrii)
>  * remove unnecessary inline functions and add comments for programs which
>    will be rejected by verifier in patch 4 (suggested by Andrii)
>  * rename variables used in will-fail programs to clarify the purposes.

Applied. Thanks