netdev - Re: [PATCH v3 bpf-next 3/4] selftest/bpf: fmod_ret prog and implement test

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Message-ID: <33778f26-8381-8607-4e14-d59c6e5f320c@fb.com>
Date:   Tue, 12 May 2020 18:10:32 -0700
From:   Yonghong Song <yhs@...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>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH v3 bpf-next 3/4] selftest/bpf: fmod_ret prog and implement
 test_overhead as part of bench



On 5/12/20 12:24 PM, 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). This slowdown seems to be coming from the fact that
> test_overhead is single-threaded, while benchmark always spins off at least
> one thread for producer. This has been confirmed by hacking multi-threaded
> test_overhead variant and also single-threaded bench variant. Resutls are
> below. run_bench_rename.sh script from benchs/ subdirectory was used to
> produce results for ./bench.
> 
> Single-threaded implementations
> ===============================
> 
> /* bench: single-threaded, atomics */
> base      :    4.622 ± 0.049M/s
> kprobe    :    3.673 ± 0.052M/s
> kretprobe :    2.625 ± 0.052M/s
> rawtp     :    4.369 ± 0.089M/s
> fentry    :    4.201 ± 0.558M/s
> fexit     :    4.309 ± 0.148M/s
> fmodret   :    4.314 ± 0.203M/s
> 
> /* selftest: single-threaded, no atomics */
> task_rename base        4555K events per sec
> task_rename kprobe      3643K events per sec
> task_rename kretprobe   2506K events per sec
> task_rename raw_tp      4303K events per sec
> task_rename fentry      4307K events per sec
> task_rename fexit       4010K events per sec
> task_rename fmod_ret    3984K events per sec
> 
> Multi-threaded implementations
> ==============================
> 
> /* bench: multi-threaded w/ atomics */
> base      :    3.910 ± 0.023M/s
> kprobe    :    3.048 ± 0.037M/s
> kretprobe :    2.300 ± 0.015M/s
> rawtp     :    3.687 ± 0.034M/s
> fentry    :    3.740 ± 0.087M/s
> fexit     :    3.510 ± 0.009M/s
> fmodret   :    3.485 ± 0.050M/s
> 
> /* selftest: multi-threaded w/ atomics */
> task_rename base        3872K events per sec
> task_rename kprobe      3068K events per sec
> task_rename kretprobe   2350K events per sec
> task_rename raw_tp      3731K events per sec
> task_rename fentry      3639K events per sec
> task_rename fexit       3558K events per sec
> task_rename fmod_ret    3511K events per sec
> 
> /* selftest: multi-threaded, no atomics */
> task_rename base        3945K events per sec
> task_rename kprobe      3298K events per sec
> task_rename kretprobe   2451K events per sec
> task_rename raw_tp      3718K events per sec
> task_rename fentry      3782K events per sec
> task_rename fexit       3543K events per sec
> task_rename fmod_ret    3526K events per sec
> 
> Note that the fact that ./bench benchmark always uses atomic increments for
> counting, while test_overhead doesn't, doesn't influence test results all that
> much.
> 
> Acked-by: John Fastabend <john.fastabend@...il.com>
> Signed-off-by: Andrii Nakryiko <andriin@...com>
Acked-by: Yonghong Song <yhs@...com>