cgroup: Add test_cpucg_weight_underprovisioned() testcase

test_cpu.c includes testcases that validate the cgroup cpu controller.
This patch adds a new testcase called test_cpucg_weight_underprovisioned()
that verifies that processes with different cpu.weight that are all running
on an underprovisioned system, still get roughly the same amount of cpu
time.

Because test_cpucg_weight_underprovisioned() is very similar to
test_cpucg_weight_overprovisioned(), this patch also pulls the common logic
into a separate helper function that is invoked from both testcases, and
which uses function pointers to invoke the unique portions of the
testcases.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/tools/testing/selftests/cgroup/test_cpu.c b/tools/testing/selftests/cgroup/test_cpu.c
index 8d901c06c79d4a97fef96f829a130ce382fc626b..64f9ce91c99231bce3393c4039b2367202b61fd1 100644 (file)
--- a/tools/testing/selftests/cgroup/test_cpu.c
+++ b/tools/testing/selftests/cgroup/test_cpu.c
@@ -19,6 +19,12 @@ enum hog_clock_type {
        CPU_HOG_CLOCK_WALL,
 };
 
+struct cpu_hogger {
+       char *cgroup;
+       pid_t pid;
+       long usage;
+};
+
 struct cpu_hog_func_param {
        int nprocs;
        struct timespec ts;
@@ -223,31 +229,15 @@ cleanup:
        return ret;
 }
 
-/*
- * First, this test creates the following hierarchy:
- * A
- * A/B     cpu.weight = 50
- * A/C     cpu.weight = 100
- * A/D     cpu.weight = 150
- *
- * A separate process is then created for each child cgroup which spawns as
- * many threads as there are cores, and hogs each CPU as much as possible
- * for some time interval.
- *
- * Once all of the children have exited, we verify that each child cgroup
- * was given proportional runtime as informed by their cpu.weight.
- */
-static int test_cpucg_weight_overprovisioned(const char *root)
+static int
+run_cpucg_weight_test(
+               const char *root,
+               pid_t (*spawn_child)(const struct cpu_hogger *child),
+               int (*validate)(const struct cpu_hogger *children, int num_children))
 {
-       struct child {
-               char *cgroup;
-               pid_t pid;
-               long usage;
-       };
        int ret = KSFT_FAIL, i;
        char *parent = NULL;
-       struct child children[3] = {NULL};
-       long usage_seconds = 10;
+       struct cpu_hogger children[3] = {NULL};
 
        parent = cg_name(root, "cpucg_test_0");
        if (!parent)
@@ -273,16 +263,7 @@ static int test_cpucg_weight_overprovisioned(const char *root)
        }
 
        for (i = 0; i < ARRAY_SIZE(children); i++) {
-               struct cpu_hog_func_param param = {
-                       .nprocs = get_nprocs(),
-                       .ts = {
-                               .tv_sec = usage_seconds,
-                               .tv_nsec = 0,
-                       },
-                       .clock_type = CPU_HOG_CLOCK_WALL,
-               };
-               pid_t pid = cg_run_nowait(children[i].cgroup, hog_cpus_timed,
-                               (void *)&param);
+               pid_t pid = spawn_child(&children[i]);
                if (pid <= 0)
                        goto cleanup;
                children[i].pid = pid;
@@ -302,7 +283,46 @@ static int test_cpucg_weight_overprovisioned(const char *root)
                children[i].usage = cg_read_key_long(children[i].cgroup,
                                "cpu.stat", "usage_usec");
 
-       for (i = 0; i < ARRAY_SIZE(children) - 1; i++) {
+       if (validate(children, ARRAY_SIZE(children)))
+               goto cleanup;
+
+       ret = KSFT_PASS;
+cleanup:
+       for (i = 0; i < ARRAY_SIZE(children); i++) {
+               cg_destroy(children[i].cgroup);
+               free(children[i].cgroup);
+       }
+       cg_destroy(parent);
+       free(parent);
+
+       return ret;
+}
+
+static pid_t weight_hog_ncpus(const struct cpu_hogger *child, int ncpus)
+{
+       long usage_seconds = 10;
+       struct cpu_hog_func_param param = {
+               .nprocs = ncpus,
+               .ts = {
+                       .tv_sec = usage_seconds,
+                       .tv_nsec = 0,
+               },
+               .clock_type = CPU_HOG_CLOCK_WALL,
+       };
+       return cg_run_nowait(child->cgroup, hog_cpus_timed, (void *)&param);
+}
+
+static pid_t weight_hog_all_cpus(const struct cpu_hogger *child)
+{
+       return weight_hog_ncpus(child, get_nprocs());
+}
+
+static int
+overprovision_validate(const struct cpu_hogger *children, int num_children)
+{
+       int ret = KSFT_FAIL, i;
+
+       for (i = 0; i < num_children - 1; i++) {
                long delta;
 
                if (children[i + 1].usage <= children[i].usage)
@@ -315,16 +335,74 @@ static int test_cpucg_weight_overprovisioned(const char *root)
 
        ret = KSFT_PASS;
 cleanup:
-       for (i = 0; i < ARRAY_SIZE(children); i++) {
-               cg_destroy(children[i].cgroup);
-               free(children[i].cgroup);
+       return ret;
+}
+
+/*
+ * First, this test creates the following hierarchy:
+ * A
+ * A/B     cpu.weight = 50
+ * A/C     cpu.weight = 100
+ * A/D     cpu.weight = 150
+ *
+ * A separate process is then created for each child cgroup which spawns as
+ * many threads as there are cores, and hogs each CPU as much as possible
+ * for some time interval.
+ *
+ * Once all of the children have exited, we verify that each child cgroup
+ * was given proportional runtime as informed by their cpu.weight.
+ */
+static int test_cpucg_weight_overprovisioned(const char *root)
+{
+       return run_cpucg_weight_test(root, weight_hog_all_cpus,
+                       overprovision_validate);
+}
+
+static pid_t weight_hog_one_cpu(const struct cpu_hogger *child)
+{
+       return weight_hog_ncpus(child, 1);
+}
+
+static int
+underprovision_validate(const struct cpu_hogger *children, int num_children)
+{
+       int ret = KSFT_FAIL, i;
+
+       for (i = 0; i < num_children - 1; i++) {
+               if (!values_close(children[i + 1].usage, children[0].usage, 15))
+                       goto cleanup;
        }
-       cg_destroy(parent);
-       free(parent);
 
+       ret = KSFT_PASS;
+cleanup:
        return ret;
 }
 
+/*
+ * First, this test creates the following hierarchy:
+ * A
+ * A/B     cpu.weight = 50
+ * A/C     cpu.weight = 100
+ * A/D     cpu.weight = 150
+ *
+ * A separate process is then created for each child cgroup which spawns a
+ * single thread that hogs a CPU. The testcase is only run on systems that
+ * have at least one core per-thread in the child processes.
+ *
+ * Once all of the children have exited, we verify that each child cgroup
+ * had roughly the same runtime despite having different cpu.weight.
+ */
+static int test_cpucg_weight_underprovisioned(const char *root)
+{
+       // Only run the test if there are enough cores to avoid overprovisioning
+       // the system.
+       if (get_nprocs() < 4)
+               return KSFT_SKIP;
+
+       return run_cpucg_weight_test(root, weight_hog_one_cpu,
+                       underprovision_validate);
+}
+
 #define T(x) { x, #x }
 struct cpucg_test {
        int (*fn)(const char *root);
@@ -333,6 +411,7 @@ struct cpucg_test {
        T(test_cpucg_subtree_control),
        T(test_cpucg_stats),
        T(test_cpucg_weight_overprovisioned),
+       T(test_cpucg_weight_underprovisioned),
 };
 #undef T