On Wed, 5 Mar 2025 at 03:04, Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> 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);
>
Ack.
> > + 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 ?
Ok.
>
> > + 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.
They do make a difference inside a VM, but not on bare-metal.
I can stick to three sizes though.
>
> > +}
> > 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?
Probably a remnant from previous versions, but sometimes if you don't do this
it gives you an error saying addr_space_cast cannot be used in a
program with no associated arena.
Probably if it never sees the arena map reference anywhere in the
program. This is a way to do that.
But in this case I dropped it and it works.
>
> > + 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
> >
