linux-kernel - Re: [PATCH bpf-next 2/2] bpf/selftests: Test pinning bpf timer to a core

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Date:   Tue, 3 Oct 2023 13:29:36 -0500
From:   David Vernet <void@...ifault.com>
To:     Song Liu <songliubraving@...a.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "andrii@...nel.org" <andrii@...nel.org>,
        "martin.lau@...ux.dev" <martin.lau@...ux.dev>,
        "song@...nel.org" <song@...nel.org>,
        "yonghong.song@...ux.dev" <yonghong.song@...ux.dev>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "kpsingh@...nel.org" <kpsingh@...nel.org>,
        "sdf@...gle.com" <sdf@...gle.com>,
        "haoluo@...gle.com" <haoluo@...gle.com>,
        "jolsa@...nel.org" <jolsa@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kernel Team <kernel-team@...a.com>,
        "himadrispandya@...il.com" <himadrispandya@...il.com>,
        "julia.lawall@...ia.fr" <julia.lawall@...ia.fr>
Subject: Re: [PATCH bpf-next 2/2] bpf/selftests: Test pinning bpf timer to a
 core

On Tue, Oct 03, 2023 at 06:15:03PM +0000, Song Liu wrote:
> 
> 
> > On Oct 2, 2023, at 4:47 PM, David Vernet <void@...ifault.com> wrote:
> > 
> > Now that we support pinning a BPF timer to the current core, we should
> > test it with some selftests. This patch adds two new testcases to the
> > timer suite, which verifies that a BPF timer both with and without
> > BPF_F_TIMER_ABS, can be pinned to the calling core with
> > BPF_F_TIMER_CPU_PIN.
> > 
> > Signed-off-by: David Vernet <void@...ifault.com>
> 
> Acked-by: Song Liu <song@...nel.org>
> 
> With one nit/question below. 
> 
> > ---
> > .../testing/selftests/bpf/prog_tests/timer.c  |  4 +
> > tools/testing/selftests/bpf/progs/timer.c     | 75 +++++++++++++++++++
> > 2 files changed, 79 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/timer.c b/tools/testing/selftests/bpf/prog_tests/timer.c
> > index 290c21dbe65a..d8bc838445ec 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/timer.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/timer.c
> > @@ -14,6 +14,7 @@ static int timer(struct timer *timer_skel)
> > 
> > ASSERT_EQ(timer_skel->data->callback_check, 52, "callback_check1");
> > ASSERT_EQ(timer_skel->data->callback2_check, 52, "callback2_check1");
> > + ASSERT_EQ(timer_skel->bss->pinned_callback_check, 0, "pinned_callback_check1");
> > 
> > prog_fd = bpf_program__fd(timer_skel->progs.test1);
> > err = bpf_prog_test_run_opts(prog_fd, &topts);
> > @@ -32,6 +33,9 @@ static int timer(struct timer *timer_skel)
> > /* check that timer_cb3() was executed twice */
> > ASSERT_EQ(timer_skel->bss->abs_data, 12, "abs_data");
> > 
> > + /* check that timer_cb_pinned() was executed twice */
> > + ASSERT_EQ(timer_skel->bss->pinned_callback_check, 2, "pinned_callback_check");
> > +
> > /* check that there were no errors in timer execution */
> > ASSERT_EQ(timer_skel->bss->err, 0, "err");
> > 
> > diff --git a/tools/testing/selftests/bpf/progs/timer.c b/tools/testing/selftests/bpf/progs/timer.c
> > index 9a16d95213e1..0112b9c038b4 100644
> > --- a/tools/testing/selftests/bpf/progs/timer.c
> > +++ b/tools/testing/selftests/bpf/progs/timer.c
> > @@ -53,12 +53,28 @@ struct {
> > __type(value, struct elem);
> > } abs_timer SEC(".maps");
> > 
> > +struct {
> > + __uint(type, BPF_MAP_TYPE_ARRAY);
> > + __uint(max_entries, 1);
> > + __type(key, int);
> > + __type(value, struct elem);
> > +} soft_timer_pinned SEC(".maps");
> > +
> > +struct {
> > + __uint(type, BPF_MAP_TYPE_ARRAY);
> > + __uint(max_entries, 1);
> > + __type(key, int);
> > + __type(value, struct elem);
> > +} abs_timer_pinned SEC(".maps");
> 
> nit: I think we can also do something like the following, but I am not 
> sure whether this style is not recommended. 
> 
> diff --git i/tools/testing/selftests/bpf/progs/timer.c w/tools/testing/selftests/bpf/progs/timer.c
> index 9a16d95213e1..638eeebcd6c9 100644
> --- i/tools/testing/selftests/bpf/progs/timer.c
> +++ w/tools/testing/selftests/bpf/progs/timer.c
> @@ -51,7 +51,7 @@ struct {
>         __uint(max_entries, 1);
>         __type(key, int);
>         __type(value, struct elem);
> -} abs_timer SEC(".maps");
> +} abs_timer SEC(".maps"), soft_timer_pinned SEC(".maps"), abs_timer_pinned SEC(".maps");

This looks like a nice readability improvement / cleanup to me. If
nobody objects, I'd say let's apply it.

Thanks,
David