netdev - RE: [PATCH bpf-next 2/3] selftest/bpf: fmod_ret prog and implement test

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Date:   Fri, 08 May 2020 08:57:47 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Andrii Nakryiko <andriin@...com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, ast@...com, daniel@...earbox.net
Cc:     andrii.nakryiko@...il.com, kernel-team@...com,
        Andrii Nakryiko <andriin@...com>
Subject: RE: [PATCH bpf-next 2/3] selftest/bpf: fmod_ret prog and implement
 test_overhead as part of bench

Andrii Nakryiko wrote:
> Add fmod_ret BPF program to existing test_overhead selftest. Also re-implement
> user-space benchmarking part into benchmark runner to compare results.  Results
> with ./bench are consistently somewhat lower than test_overhead's, but relative
> performance of various types of BPF programs stay consisten (e.g., kretprobe is
> noticeably slower).
> 
> To test with ./bench, the following command was used:
> 
> for i in base kprobe kretprobe rawtp fentry fexit fmodret; \
> do \
>     summary=$(sudo ./bench -w2 -d5 -a rename-$i | \
>               tail -n1 | cut -d'(' -f1 | cut -d' ' -f3-) && \
>     printf "%-10s: %s\n" $i "$summary"; \
> done

might be nice to have a script ./bench_tracing_overhead.sh when its in its
own directory ./bench. Otherwise I'll have to look this up every single
time I'm sure.

> 
> This gives the following numbers:
> 
>   base      :    3.975 ± 0.065M/s
>   kprobe    :    3.268 ± 0.095M/s
>   kretprobe :    2.496 ± 0.040M/s
>   rawtp     :    3.899 ± 0.078M/s
>   fentry    :    3.836 ± 0.049M/s
>   fexit     :    3.660 ± 0.082M/s
>   fmodret   :    3.776 ± 0.033M/s
> 
> While running test_overhead gives:
> 
>   task_rename base        4457K events per sec
>   task_rename kprobe      3849K events per sec
>   task_rename kretprobe   2729K events per sec
>   task_rename raw_tp      4506K events per sec
>   task_rename fentry      4381K events per sec
>   task_rename fexit       4349K events per sec
>   task_rename fmod_ret    4130K events per sec
> 
> Signed-off-by: Andrii Nakryiko <andriin@...com>
> ---

LGTM

Acked-by: John Fastabend <john.fastabend@...il.com>