test_kmem.c

// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE

#include <linux/limits.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>
#include <errno.h>
#include <sys/sysinfo.h>
#include <pthread.h>

#include "../kselftest.h"
#include "cgroup_util.h"


/*
 * Memory cgroup charging is performed using percpu batches 64 pages
 * big (look at MEMCG_CHARGE_BATCH), whereas memory.stat is exact. So
 * the maximum discrepancy between charge and vmstat entries is number
 * of cpus multiplied by 64 pages.
 */
#define MAX_VMSTAT_ERROR (4096 * 64 * get_nprocs())


static int alloc_dcache(const char *cgroup, void *arg)
{
	unsigned long i;
	struct stat st;
	char buf[128];

	for (i = 0; i < (unsigned long)arg; i++) {
		snprintf(buf, sizeof(buf),
			"/something-non-existent-with-a-long-name-%64lu-%d",
			 i, getpid());
		stat(buf, &st);
	}

	return 0;
}

/*
 * This test allocates 100000 of negative dentries with long names.
 * Then it checks that "slab" in memory.stat is larger than 1M.
 * Then it sets memory.high to 1M and checks that at least 1/2
 * of slab memory has been reclaimed.
 */
static int test_kmem_basic(const char *root)
{
	int ret = KSFT_FAIL;
	char *cg = NULL;
	long slab0, slab1, current;

	cg = cg_name(root, "kmem_basic_test");
	if (!cg)
		goto cleanup;

	if (cg_create(cg))
		goto cleanup;

	if (cg_run(cg, alloc_dcache, (void *)100000))
		goto cleanup;

	slab0 = cg_read_key_long(cg, "memory.stat", "slab ");
	if (slab0 < (1 << 20))
		goto cleanup;

	cg_write(cg, "memory.high", "1M");

	/* wait for RCU freeing */
	sleep(1);

	slab1 = cg_read_key_long(cg, "memory.stat", "slab ");
	if (slab1 < 0)
		goto cleanup;

	current = cg_read_long(cg, "memory.current");
	if (current < 0)
		goto cleanup;

	if (slab1 < slab0 / 2 && current < slab0 / 2)
		ret = KSFT_PASS;
cleanup:
	cg_destroy(cg);
	free(cg);

	return ret;
}

static void *alloc_kmem_fn(void *arg)
{
	alloc_dcache(NULL, (void *)100);
	return NULL;
}

static int alloc_kmem_smp(const char *cgroup, void *arg)
{
	int nr_threads = 2 * get_nprocs();
	pthread_t *tinfo;
	unsigned long i;
	int ret = -1;

	tinfo = calloc(nr_threads, sizeof(pthread_t));
	if (tinfo == NULL)
		return -1;

	for (i = 0; i < nr_threads; i++) {
		if (pthread_create(&tinfo[i], NULL, &alloc_kmem_fn,
				   (void *)i)) {
			free(tinfo);
			return -1;
		}
	}

	for (i = 0; i < nr_threads; i++) {
		ret = pthread_join(tinfo[i], NULL);
		if (ret)
			break;
	}

	free(tinfo);
	return ret;
}

static int cg_run_in_subcgroups(const char *parent,
				int (*fn)(const char *cgroup, void *arg),
				void *arg, int times)
{
	char *child;
	int i;

	for (i = 0; i < times; i++) {
		child = cg_name_indexed(parent, "child", i);
		if (!child)
			return -1;

		if (cg_create(child)) {
			cg_destroy(child);
			free(child);
			return -1;
		}

		if (cg_run(child, fn, NULL)) {
			cg_destroy(child);
			free(child);
			return -1;
		}

		cg_destroy(child);
		free(child);
	}

	return 0;
}

/*
 * The test creates and destroys a large number of cgroups. In each cgroup it
 * allocates some slab memory (mostly negative dentries) using 2 * NR_CPUS
 * threads. Then it checks the sanity of numbers on the parent level:
 * the total size of the cgroups should be roughly equal to
 * anon + file + kernel + sock.
 */
static int test_kmem_memcg_deletion(const char *root)
{
	long current, anon, file, kernel, sock, sum;
	int ret = KSFT_FAIL;
	char *parent;

	parent = cg_name(root, "kmem_memcg_deletion_test");
	if (!parent)
		goto cleanup;

	if (cg_create(parent))
		goto cleanup;

	if (cg_write(parent, "cgroup.subtree_control", "+memory"))
		goto cleanup;

	if (cg_run_in_subcgroups(parent, alloc_kmem_smp, NULL, 100))
		goto cleanup;

	current = cg_read_long(parent, "memory.current");
	anon = cg_read_key_long(parent, "memory.stat", "anon ");
	file = cg_read_key_long(parent, "memory.stat", "file ");
	kernel = cg_read_key_long(parent, "memory.stat", "kernel ");
	sock = cg_read_key_long(parent, "memory.stat", "sock ");
	if (current < 0 || anon < 0 || file < 0 || kernel < 0 || sock < 0)
		goto cleanup;

	sum = anon + file + kernel + sock;
	if (labs(sum - current) < MAX_VMSTAT_ERROR) {
		ret = KSFT_PASS;
	} else {
		printf("memory.current = %ld\n", current);
		printf("anon + file + kernel + sock = %ld\n", sum);
		printf("anon = %ld\n", anon);
		printf("file = %ld\n", file);
		printf("kernel = %ld\n", kernel);
		printf("sock = %ld\n", sock);
	}

cleanup:
	cg_destroy(parent);
	free(parent);

	return ret;
}

/*
 * The test reads the entire /proc/kpagecgroup. If the operation went
 * successfully (and the kernel didn't panic), the test is treated as passed.
 */
static int test_kmem_proc_kpagecgroup(const char *root)
{
	unsigned long buf[128];
	int ret = KSFT_FAIL;
	ssize_t len;
	int fd;

	fd = open("/proc/kpagecgroup", O_RDONLY);
	if (fd < 0)
		return ret;

	do {
		len = read(fd, buf, sizeof(buf));
	} while (len > 0);

	if (len == 0)
		ret = KSFT_PASS;

	close(fd);
	return ret;
}

static void *pthread_wait_fn(void *arg)
{
	sleep(100);
	return NULL;
}

static int spawn_1000_threads(const char *cgroup, void *arg)
{
	int nr_threads = 1000;
	pthread_t *tinfo;
	unsigned long i;
	long stack;
	int ret = -1;

	tinfo = calloc(nr_threads, sizeof(pthread_t));
	if (tinfo == NULL)
		return -1;

	for (i = 0; i < nr_threads; i++) {
		if (pthread_create(&tinfo[i], NULL, &pthread_wait_fn,
				   (void *)i)) {
			free(tinfo);
			return(-1);
		}
	}

	stack = cg_read_key_long(cgroup, "memory.stat", "kernel_stack ");
	if (stack >= 4096 * 1000)
		ret = 0;

	free(tinfo);
	return ret;
}

/*
 * The test spawns a process, which spawns 1000 threads. Then it checks
 * that memory.stat's kernel_stack is at least 1000 pages large.
 */
static int test_kmem_kernel_stacks(const char *root)
{
	int ret = KSFT_FAIL;
	char *cg = NULL;

	cg = cg_name(root, "kmem_kernel_stacks_test");
	if (!cg)
		goto cleanup;

	if (cg_create(cg))
		goto cleanup;

	if (cg_run(cg, spawn_1000_threads, NULL))
		goto cleanup;

	ret = KSFT_PASS;
cleanup:
	cg_destroy(cg);
	free(cg);

	return ret;
}

/*
 * This test sequentionally creates 30 child cgroups, allocates some
 * kernel memory in each of them, and deletes them. Then it checks
 * that the number of dying cgroups on the parent level is 0.
 */
static int test_kmem_dead_cgroups(const char *root)
{
	int ret = KSFT_FAIL;
	char *parent;
	long dead;
	int i;
	int max_time = 20;

	parent = cg_name(root, "kmem_dead_cgroups_test");
	if (!parent)
		goto cleanup;

	if (cg_create(parent))
		goto cleanup;

	if (cg_write(parent, "cgroup.subtree_control", "+memory"))
		goto cleanup;

	if (cg_run_in_subcgroups(parent, alloc_dcache, (void *)100, 30))
		goto cleanup;

	for (i = 0; i < max_time; i++) {
		dead = cg_read_key_long(parent, "cgroup.stat",
					"nr_dying_descendants ");
		if (dead == 0) {
			ret = KSFT_PASS;
			break;
		}
		/*
		 * Reclaiming cgroups might take some time,
		 * let's wait a bit and repeat.
		 */
		sleep(1);
		if (i > 5)
			printf("Waiting time longer than 5s; wait: %ds (dead: %ld)\n", i, dead);
	}

cleanup:
	cg_destroy(parent);
	free(parent);

	return ret;
}

/*
 * This test creates a sub-tree with 1000 memory cgroups.
 * Then it checks that the memory.current on the parent level
 * is greater than 0 and approximates matches the percpu value
 * from memory.stat.
 */
static int test_percpu_basic(const char *root)
{
	int ret = KSFT_FAIL;
	char *parent, *child;
	long current, percpu;
	int i;

	parent = cg_name(root, "percpu_basic_test");
	if (!parent)
		goto cleanup;

	if (cg_create(parent))
		goto cleanup;

	if (cg_write(parent, "cgroup.subtree_control", "+memory"))
		goto cleanup;

	for (i = 0; i < 1000; i++) {
		child = cg_name_indexed(parent, "child", i);
		if (!child)
			return -1;

		if (cg_create(child))
			goto cleanup_children;

		free(child);
	}

	current = cg_read_long(parent, "memory.current");
	percpu = cg_read_key_long(parent, "memory.stat", "percpu ");

	if (current > 0 && percpu > 0 && labs(current - percpu) <
	    MAX_VMSTAT_ERROR)
		ret = KSFT_PASS;
	else
		printf("memory.current %ld\npercpu %ld\n",
		       current, percpu);

cleanup_children:
	for (i = 0; i < 1000; i++) {
		child = cg_name_indexed(parent, "child", i);
		cg_destroy(child);
		free(child);
	}

cleanup:
	cg_destroy(parent);
	free(parent);

	return ret;
}

#define T(x) { x, #x }
struct kmem_test {
	int (*fn)(const char *root);
	const char *name;
} tests[] = {
	T(test_kmem_basic),
	T(test_kmem_memcg_deletion),
	T(test_kmem_proc_kpagecgroup),
	T(test_kmem_kernel_stacks),
	T(test_kmem_dead_cgroups),
	T(test_percpu_basic),
};
#undef T

int main(int argc, char **argv)
{
	char root[PATH_MAX];
	int i, ret = EXIT_SUCCESS;

	if (cg_find_unified_root(root, sizeof(root), NULL))
		ksft_exit_skip("cgroup v2 isn't mounted\n");

	/*
	 * Check that memory controller is available:
	 * memory is listed in cgroup.controllers
	 */
	if (cg_read_strstr(root, "cgroup.controllers", "memory"))
		ksft_exit_skip("memory controller isn't available\n");

	if (cg_read_strstr(root, "cgroup.subtree_control", "memory"))
		if (cg_write(root, "cgroup.subtree_control", "+memory"))
			ksft_exit_skip("Failed to set memory controller\n");

	for (i = 0; i < ARRAY_SIZE(tests); i++) {
		switch (tests[i].fn(root)) {
		case KSFT_PASS:
			ksft_test_result_pass("%s\n", tests[i].name);
			break;
		case KSFT_SKIP:
			ksft_test_result_skip("%s\n", tests[i].name);
			break;
		default:
			ret = EXIT_FAILURE;
			ksft_test_result_fail("%s\n", tests[i].name);
			break;
		}
	}

	return ret;
}