linux-kernel - Re: [PATCH] selftests/bpf: Add LPM trie microbenchmarks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAENh_ST_8XN2+QT8xz1gcKyovwEGwO-j2-YHbMj6GrWuZcgRag@mail.gmail.com>
Date: Mon, 21 Jul 2025 14:01:32 +0100
From: Matt Fleming <matt@...dmodwrite.com>
To: Jesper Dangaard Brouer <hawk@...nel.org>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>, 
	Martin KaFai Lau <martin.lau@...nel.org>, Shuah Khan <shuah@...nel.org>, kernel-team@...udflare.com, 
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org, Matt Fleming <mfleming@...udflare.com>, 
	Yonghong Song <yonghong.song@...ux.dev>, Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] selftests/bpf: Add LPM trie microbenchmarks

On Sat, Jul 19, 2025 at 2:15 PM Jesper Dangaard Brouer <hawk@...nel.org> wrote:
>
> On 18/07/2025 17.05, Matt Fleming wrote:
>
> > [...]
> > diff --git a/tools/testing/selftests/bpf/progs/lpm_trie_bench.c b/tools/testing/selftests/bpf/progs/lpm_trie_bench.c
> > new file mode 100644
> > index 000000000000..c335718cc240
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/lpm_trie_bench.c
> > @@ -0,0 +1,175 @@
> [...]
> > +
> > +static __always_inline void atomic_inc(long *cnt)
> > +{
> > +     __atomic_add_fetch(cnt, 1, __ATOMIC_SEQ_CST);
> > +}
> > +
> > +static __always_inline long atomic_swap(long *cnt, long val)
> > +{
> > +     return __atomic_exchange_n(cnt, val, __ATOMIC_SEQ_CST);
> > +}
>
> For userspace includes we have similar defines in bench.h.
> Except they use __ATOMIC_RELAXED and here __ATOMIC_SEQ_CST.
> Which is the correct to use?
>
> For BPF kernel-side do selftests have another header file that define
> these `atomic_inc` and `atomic_swap` ?

Actually, we can side step this problem completely by consistently
using __sync_fetch_and_add() for duration_ns and hits and removing the
atomic operations for DELETE, which doesn't need atomicity anyway
since only a single producer can run.

I'll send a v2.