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cgroup/rstat: Selftests for niced CPU statistics

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Creates a cgroup with a single nice CPU hog process running.
fork() is called to generate the nice process because un-nicing is
not possible (see man nice(3)). If fork() was not used to generate
the CPU hog, we would run the rest of the cgroup selftest suite as a
nice process.

Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Joshua Hahn 2024-10-02 11:47:17 -07:00 • committed by Tejun Heo
parent aefa398d93
commit 2e82c0d456
1 changed files with 75 additions and 0 deletions
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75
tools/testing/selftests/cgroup/test_cpu.c
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@ -8,6 +8,7 @@
#include <pthread.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>
#include "../kselftest.h"
#include "cgroup_util.h"
@ -229,6 +230,79 @@ cleanup:
return ret;
}
/*
* Creates a nice process that consumes CPU and checks that the elapsed
* usertime in the cgroup is close to the expected time.
*/
static int test_cpucg_nice(const char *root)
{
int ret = KSFT_FAIL;
int status;
long user_usec, nice_usec;
long usage_seconds = 2;
long expected_nice_usec = usage_seconds * USEC_PER_SEC;
char *cpucg;
pid_t pid;
cpucg = cg_name(root, "cpucg_test");
if (!cpucg)
goto cleanup;
if (cg_create(cpucg))
goto cleanup;
user_usec = cg_read_key_long(cpucg, "cpu.stat", "user_usec");
nice_usec = cg_read_key_long(cpucg, "cpu.stat", "nice_usec");
if (nice_usec == -1)
ret = KSFT_SKIP;
if (user_usec != 0 || nice_usec != 0)
goto cleanup;
/*
* We fork here to create a new process that can be niced without
* polluting the nice value of other selftests
*/
pid = fork();
if (pid < 0) {
goto cleanup;
} else if (pid == 0) {
struct cpu_hog_func_param param = {
.nprocs = 1,
.ts = {
.tv_sec = usage_seconds,
.tv_nsec = 0,
},
.clock_type = CPU_HOG_CLOCK_PROCESS,
};
char buf[64];
snprintf(buf, sizeof(buf), "%d", getpid());
if (cg_write(cpucg, "cgroup.procs", buf))
goto cleanup;
/* Try to keep niced CPU usage as constrained to hog_cpu as possible */
nice(1);
hog_cpus_timed(cpucg, param);
exit(0);
} else {
waitpid(pid, &status, 0);
if (!WIFEXITED(status))
goto cleanup;
user_usec = cg_read_key_long(cpucg, "cpu.stat", "user_usec");
nice_usec = cg_read_key_long(cpucg, "cpu.stat", "nice_usec");
if (!values_close(nice_usec, expected_nice_usec, 1))
goto cleanup;
ret = KSFT_PASS;
}
cleanup:
cg_destroy(cpucg);
free(cpucg);
return ret;
}
static int
run_cpucg_weight_test(
const char *root,
@ -686,6 +760,7 @@ struct cpucg_test {
} tests[] = {
T(test_cpucg_subtree_control),
T(test_cpucg_stats),
T(test_cpucg_nice),
T(test_cpucg_weight_overprovisioned),
T(test_cpucg_weight_underprovisioned),
T(test_cpucg_nested_weight_overprovisioned),