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selftests/bpf: Add selftests for cpumask iter
Within the BPF program, we leverage the cgroup iterator to iterate through percpu runqueue data, specifically the 'nr_running' metric. Subsequently we expose this data to userspace by means of a sequence file. The CPU affinity for the cpumask is determined by the PID of a task: - PID of the init task (PID 1) We typically don't set CPU affinity for init task and thus we can iterate across all possible CPUs. However, in scenarios where you've set CPU affinity for the init task, you should set the cpumask of your current task to full-F. Then proceed to iterate through all possible CPUs using the current task. - PID of a task with defined CPU affinity The aim here is to iterate through a specific cpumask. This scenario aligns with tasks residing within a cpuset cgroup. - Invalid PID (e.g., PID -1) No cpumask is available in this case. The result as follows, torvalds#62/1 cpumask_iter/init_pid:OK torvalds#62/2 cpumask_iter/invalid_pid:OK torvalds#62/3 cpumask_iter/self_pid_one_cpu:OK torvalds#62/4 cpumask_iter/self_pid_multi_cpus:OK torvalds#62 cpumask_iter:OK Summary: 1/4 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
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// SPDX-License-Identifier: GPL-2.0 | ||
/* Copyright (c) 2023 Yafang Shao <laoar.shao@gmail.com> */ | ||
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#define _GNU_SOURCE | ||
#include <sched.h> | ||
#include <stdio.h> | ||
#include <unistd.h> | ||
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#include <test_progs.h> | ||
#include "cgroup_helpers.h" | ||
#include "test_cpumask_iter.skel.h" | ||
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static void verify_percpu_data(struct bpf_link *link, int nr_cpu_exp, int nr_running_exp) | ||
{ | ||
int iter_fd, len, item, nr_running, nr_cpus; | ||
static char buf[128]; | ||
size_t left; | ||
char *p; | ||
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iter_fd = bpf_iter_create(bpf_link__fd(link)); | ||
if (!ASSERT_GE(iter_fd, 0, "iter_fd")) | ||
return; | ||
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memset(buf, 0, sizeof(buf)); | ||
left = ARRAY_SIZE(buf); | ||
p = buf; | ||
while ((len = read(iter_fd, p, left)) > 0) { | ||
p += len; | ||
left -= len; | ||
} | ||
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item = sscanf(buf, "nr_running %u nr_cpus %u\n", &nr_running, &nr_cpus); | ||
if (nr_cpu_exp == -1) { | ||
ASSERT_EQ(item, -1, "seq_format"); | ||
goto out; | ||
} | ||
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ASSERT_EQ(item, 2, "seq_format"); | ||
ASSERT_GE(nr_running, nr_running_exp, "nr_running"); | ||
ASSERT_EQ(nr_cpus, nr_cpu_exp, "nr_cpus"); | ||
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/* read() after iter finishes should be ok. */ | ||
if (len == 0) | ||
ASSERT_OK(read(iter_fd, buf, sizeof(buf)), "second_read"); | ||
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out: | ||
close(iter_fd); | ||
} | ||
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void test_cpumask_iter(void) | ||
{ | ||
DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts); | ||
int nr_possible, cgrp_fd, pid, err, cnt, i; | ||
struct test_cpumask_iter *skel = NULL; | ||
union bpf_iter_link_info linfo; | ||
int cpu_ids[] = {1, 3, 4, 5}; | ||
struct bpf_link *link; | ||
cpu_set_t set; | ||
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skel = test_cpumask_iter__open_and_load(); | ||
if (!ASSERT_OK_PTR(skel, "test_for_each_cpu__open_and_load")) | ||
return; | ||
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if (setup_cgroup_environment()) | ||
goto destroy; | ||
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/* Utilize the cgroup iter */ | ||
cgrp_fd = get_root_cgroup(); | ||
if (!ASSERT_GE(cgrp_fd, 0, "create cgrp")) | ||
goto cleanup; | ||
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memset(&linfo, 0, sizeof(linfo)); | ||
linfo.cgroup.cgroup_fd = cgrp_fd; | ||
linfo.cgroup.order = BPF_CGROUP_ITER_SELF_ONLY; | ||
opts.link_info = &linfo; | ||
opts.link_info_len = sizeof(linfo); | ||
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link = bpf_program__attach_iter(skel->progs.cpu_cgroup, &opts); | ||
if (!ASSERT_OK_PTR(link, "attach_iter")) | ||
goto close_fd; | ||
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skel->bss->target_pid = 1; | ||
/* In case init task is set CPU affinity */ | ||
err = sched_getaffinity(1, sizeof(set), &set); | ||
if (!ASSERT_OK(err, "setaffinity")) | ||
goto close_fd; | ||
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cnt = CPU_COUNT(&set); | ||
nr_possible = bpf_num_possible_cpus(); | ||
if (test__start_subtest("init_pid")) | ||
/* curent task is running. */ | ||
verify_percpu_data(link, cnt, cnt == nr_possible ? 1 : 0); | ||
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skel->bss->target_pid = -1; | ||
if (test__start_subtest("invalid_pid")) | ||
verify_percpu_data(link, -1, -1); | ||
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pid = getpid(); | ||
skel->bss->target_pid = pid; | ||
CPU_ZERO(&set); | ||
CPU_SET(0, &set); | ||
err = sched_setaffinity(pid, sizeof(set), &set); | ||
if (!ASSERT_OK(err, "setaffinity")) | ||
goto free_link; | ||
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if (test__start_subtest("self_pid_one_cpu")) | ||
verify_percpu_data(link, 1, 1); | ||
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/* Assume there are at least 8 CPUs on the testbed */ | ||
if (nr_possible < 8) | ||
goto free_link; | ||
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CPU_ZERO(&set); | ||
/* Set the CPU affinitiy: 1,3-5 */ | ||
for (i = 0; i < ARRAY_SIZE(cpu_ids); i++) | ||
CPU_SET(cpu_ids[i], &set); | ||
err = sched_setaffinity(pid, sizeof(set), &set); | ||
if (!ASSERT_OK(err, "setaffinity")) | ||
goto free_link; | ||
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if (test__start_subtest("self_pid_multi_cpus")) | ||
verify_percpu_data(link, ARRAY_SIZE(cpu_ids), 1); | ||
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free_link: | ||
bpf_link__destroy(link); | ||
close_fd: | ||
close(cgrp_fd); | ||
cleanup: | ||
cleanup_cgroup_environment(); | ||
destroy: | ||
test_cpumask_iter__destroy(skel); | ||
} |
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// SPDX-License-Identifier: GPL-2.0-only | ||
/* Copyright (c) 2023 Yafang Shao <laoar.shao@gmail.com> */ | ||
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#include "vmlinux.h" | ||
#include <bpf/bpf_helpers.h> | ||
#include <bpf/bpf_tracing.h> | ||
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#include "cpumask_common.h" | ||
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extern const struct rq runqueues __ksym __weak; | ||
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int target_pid; | ||
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SEC("iter/cgroup") | ||
int BPF_PROG(cpu_cgroup, struct bpf_iter_meta *meta, struct cgroup *cgrp) | ||
{ | ||
u32 *cpu, nr_running = 0, nr_cpus = 0; | ||
struct bpf_cpumask *mask; | ||
struct rq *rq; | ||
int ret; | ||
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/* epilogue */ | ||
if (cgrp == NULL) | ||
return 0; | ||
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mask = bpf_cpumask_create(); | ||
if (!mask) | ||
return 1; | ||
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ret = bpf_cpumask_set_from_pid(&mask->cpumask, target_pid); | ||
if (ret == false) { | ||
bpf_cpumask_release(mask); | ||
return 1; | ||
} | ||
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bpf_for_each(cpumask, cpu, &mask->cpumask) { | ||
rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, *cpu); | ||
if (!rq) | ||
continue; | ||
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nr_running += rq->nr_running; | ||
nr_cpus += 1; | ||
} | ||
BPF_SEQ_PRINTF(meta->seq, "nr_running %u nr_cpus %u\n", nr_running, nr_cpus); | ||
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bpf_cpumask_release(mask); | ||
return 0; | ||
} | ||
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char _license[] SEC("license") = "GPL"; |