On Tue, Mar 4, 2025 at 5:18 PM Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> wrote:
>
> Add some basic selftests for qspinlock built over BPF arena using
> cond_break_label macro.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> ---
> .../bpf/prog_tests/arena_spin_lock.c | 102 ++++++++++++++++++
> .../selftests/bpf/progs/arena_spin_lock.c | 51 +++++++++
> 2 files changed, 153 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c
> create mode 100644 tools/testing/selftests/bpf/progs/arena_spin_lock.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c b/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c
> new file mode 100644
> index 000000000000..2cc078ed1ddb
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c
> @@ -0,0 +1,102 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
> +#include <test_progs.h>
> +#include <network_helpers.h>
> +#include <sys/sysinfo.h>
> +
> +struct qspinlock { int val; };
> +typedef struct qspinlock arena_spinlock_t;
> +
> +struct arena_qnode {
> + unsigned long next;
> + int count;
> + int locked;
> +};
> +
> +#include "arena_spin_lock.skel.h"
> +
> +static long cpu;
> +int *counter;
> +
> +static void *spin_lock_thread(void *arg)
> +{
> + int err, prog_fd = *(u32 *)arg;
> + LIBBPF_OPTS(bpf_test_run_opts, topts,
> + .data_in = &pkt_v4,
> + .data_size_in = sizeof(pkt_v4),
> + .repeat = 1,
> + );
Why bother with 'tc' prog type?
Pick syscall type, and above will be shorter:
LIBBPF_OPTS(bpf_test_run_opts, opts);
> + cpu_set_t cpuset;
> +
> + CPU_ZERO(&cpuset);
> + CPU_SET(__sync_fetch_and_add(&cpu, 1), &cpuset);
> + ASSERT_OK(pthread_setaffinity_np(pthread_self(), sizeof(cpuset), &cpuset), "cpu affinity");
> +
> + while (*READ_ONCE(counter) <= 1000) {
READ_ONCE(*counter) ?
but why add this user->kernel switch overhead.
Use .repeat = 1000
one bpf_prog_test_run_opts()
and check at the end that *counter == 1000 ?
> + err = bpf_prog_test_run_opts(prog_fd, &topts);
> + if (!ASSERT_OK(err, "test_run err"))
> + break;
> + if (!ASSERT_EQ((int)topts.retval, 0, "test_run retval"))
> + break;
> + }
> + pthread_exit(arg);
> +}
> +
> +static void test_arena_spin_lock_size(int size)
> +{
> + LIBBPF_OPTS(bpf_test_run_opts, topts);
> + struct arena_spin_lock *skel;
> + pthread_t thread_id[16];
> + int prog_fd, i, err;
> + void *ret;
> +
> + if (get_nprocs() < 2) {
> + test__skip();
> + return;
> + }
> +
> + skel = arena_spin_lock__open_and_load();
> + if (!ASSERT_OK_PTR(skel, "arena_spin_lock__open_and_load"))
> + return;
> + if (skel->data->test_skip == 2) {
> + test__skip();
> + goto end;
> + }
> + counter = &skel->bss->counter;
> + skel->bss->cs_count = size;
> +
> + prog_fd = bpf_program__fd(skel->progs.prog);
> + for (i = 0; i < 16; i++) {
> + err = pthread_create(&thread_id[i], NULL, &spin_lock_thread, &prog_fd);
> + if (!ASSERT_OK(err, "pthread_create"))
> + goto end;
> + }
> +
> + for (i = 0; i < 16; i++) {
> + if (!ASSERT_OK(pthread_join(thread_id[i], &ret), "pthread_join"))
> + goto end;
> + if (!ASSERT_EQ(ret, &prog_fd, "ret == prog_fd"))
> + goto end;
> + }
> +end:
> + arena_spin_lock__destroy(skel);
> + return;
> +}
> +
> +void test_arena_spin_lock(void)
> +{
> + if (test__start_subtest("arena_spin_lock_1"))
> + test_arena_spin_lock_size(1);
> + cpu = 0;
> + if (test__start_subtest("arena_spin_lock_1000"))
> + test_arena_spin_lock_size(1000);
> + cpu = 0;
> + if (test__start_subtest("arena_spin_lock_10000"))
> + test_arena_spin_lock_size(10000);
> + cpu = 0;
> + if (test__start_subtest("arena_spin_lock_100000"))
> + test_arena_spin_lock_size(100000);
> + cpu = 0;
> + if (test__start_subtest("arena_spin_lock_500000"))
> + test_arena_spin_lock_size(500000);
Do 10k and 500k make a difference?
I suspect 1, 1k and 100k would cover the interesting range.
> +}
> diff --git a/tools/testing/selftests/bpf/progs/arena_spin_lock.c b/tools/testing/selftests/bpf/progs/arena_spin_lock.c
> new file mode 100644
> index 000000000000..3e8ce807e028
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/arena_spin_lock.c
> @@ -0,0 +1,51 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
> +#include <vmlinux.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +#include "bpf_misc.h"
> +#include "bpf_arena_spin_lock.h"
> +
> +struct {
> + __uint(type, BPF_MAP_TYPE_ARENA);
> + __uint(map_flags, BPF_F_MMAPABLE);
> + __uint(max_entries, 100); /* number of pages */
> +#ifdef __TARGET_ARCH_arm64
> + __ulong(map_extra, 0x1ull << 32); /* start of mmap() region */
> +#else
> + __ulong(map_extra, 0x1ull << 44); /* start of mmap() region */
> +#endif
> +} arena SEC(".maps");
> +
> +int cs_count;
> +
> +#if defined(ENABLE_ATOMICS_TESTS) && defined(__BPF_FEATURE_ADDR_SPACE_CAST)
> +arena_spinlock_t __arena lock;
> +void *ptr;
> +int test_skip = 1;
> +#else
> +int test_skip = 2;
> +#endif
> +
> +int counter;
> +
> +SEC("tc")
> +int prog(void *ctx)
> +{
> + int ret = -2;
> +
> +#if defined(ENABLE_ATOMICS_TESTS) && defined(__BPF_FEATURE_ADDR_SPACE_CAST)
> + unsigned long flags;
> +
> + ptr = &arena;
Is it really necessary?
> + if ((ret = arena_spin_lock_irqsave(&lock, flags)))
> + return ret;
> + WRITE_ONCE(counter, READ_ONCE(counter) + 1);
> + bpf_repeat(cs_count);
> + ret = 0;
> + arena_spin_unlock_irqrestore(&lock, flags);
> +#endif
> + return ret;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.47.1
>
