[PATCH RFC 2/8] selftests: add stress testing tool for dcache

Konstantin Khlebnikov
2020-05-08T12:23:23Z

This tool fills dcache with negative dentries. Between iterations it prints
statistics and measures time of inotify operation which might degrade.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
tools/testing/selftests/filesystems/Makefile | 1
.../testing/selftests/filesystems/dcache_stress.c | 210 ++++++++++++++++++++
2 files changed, 211 insertions(+)
create mode 100644 tools/testing/selftests/filesystems/dcache_stress.c

diff --git a/tools/testing/selftests/filesystems/Makefile b/tools/testing/selftests/filesystems/Makefile
index 129880fb42d3..6b5e08617d11 100644
--- a/tools/testing/selftests/filesystems/Makefile
+++ b/tools/testing/selftests/filesystems/Makefile
@@ -3,5 +3,6 @@
CFLAGS += -I../../../../usr/include/
TEST_GEN_PROGS := devpts_pts
TEST_GEN_PROGS_EXTENDED := dnotify_test
+TEST_GEN_FILES += dcache_stress

include ../lib.mk
diff --git a/tools/testing/selftests/filesystems/dcache_stress.c b/tools/testing/selftests/filesystems/dcache_stress.c
new file mode 100644
index 000000000000..770e8876629e
--- /dev/null
+++ b/tools/testing/selftests/filesystems/dcache_stress.c
@@ -0,0 +1,210 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/inotify.h>
+#include <sys/stat.h>
+#include <time.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <string.h>
+#include <err.h>
+
+double now(void)
+{
+ struct timespec ts;
+
+ clock_gettime(CLOCK_MONOTONIC, &ts);
+ return ts.tv_sec + ts.tv_nsec * 1e-9;
+}
+
+struct dentry_stat {
+ long nr_dentry;
+ long nr_unused;
+ long age_limit; /* age in seconds */
+ long want_pages; /* pages requested by system */
+ long nr_negative; /* # of unused negative dentries */
+ long nr_buckets; /* count of dcache hash buckets */
+};
+
+void show_dentry_state(void)
+{
+ struct dentry_stat stat;
+ ssize_t len;
+ FILE *f;
+
+ f = fopen("/proc/sys/fs/dentry-state", "r");
+ if (!f)
+ err(2, "open fs.dentry-state");
+
+ if (fscanf(f, "%ld %ld %ld %ld %ld %ld",
+ &stat.nr_dentry,
+ &stat.nr_unused,
+ &stat.age_limit,
+ &stat.want_pages,
+ &stat.nr_negative,
+ &stat.nr_buckets) != 6)
+ err(2, "read fs.dentry-state");
+ fclose(f);
+
+ if (!stat.nr_buckets)
+ stat.nr_buckets = 1 << 20; // for 8Gb ram
+
+ printf("nr_dentry = %ld\t%.1fM\n", stat.nr_dentry, stat.nr_dentry / 1e6);
+ printf("nr_buckets = %ld\t%.1f avg\n", stat.nr_buckets, (double)stat.nr_dentry / stat.nr_buckets);
+ printf("nr_unused = %ld\t%.1f%%\n", stat.nr_unused, stat.nr_unused * 100. / stat.nr_dentry);
+ printf("nr_negative = %ld\t%.1f%%\n\n", stat.nr_negative, stat.nr_negative * 100. / stat.nr_dentry);
+}
+
+void test_inotify(const char *path)
+{
+ double tm;
+ int fd;
+
+ fd = inotify_init1(0);
+
+ tm = now();
+ inotify_add_watch(fd, path, IN_OPEN);
+ tm = now() - tm;
+
+ printf("inotify time: %f seconds\n\n", tm);
+
+ close(fd);
+}
+
+int main(int argc, char **argv)
+{
+ char dir_name[] = "dcache_stress.XXXXXX";
+ char name[4096];
+ char *suffix = name;
+ int nr_iterations = 10;
+ int nr_names = 1 << 20;
+ int iteration, index;
+ int other_dir = -1;
+ int mknod_unlink = 0;
+ int mkdir_chdir = 0;
+ int second_access = 0;
+ long long total_names = 0;
+ double tm;
+ int opt;
+
+ while ((opt = getopt(argc, argv, "i:n:p:o:usdh")) != -1) {
+ switch (opt) {
+ case 'i':
+ nr_iterations = atoi(optarg);
+ break;
+ case 'n':
+ nr_names = atoi(optarg);
+ break;
+ case 'p':
+ strcpy(suffix, optarg);
+ suffix += strlen(suffix);
+ break;
+ case 'o':
+ other_dir = open(optarg, O_RDONLY | O_DIRECTORY);
+ if (other_dir < 0)
+ err(2, "open %s", optarg);
+ break;
+ case 'u':
+ mknod_unlink = 1;
+ break;
+ case 'd':
+ mkdir_chdir = 1;
+ break;
+ case 's':
+ second_access = 1;
+ break;
+ case '?':
+ case 'h':
+ printf("usage: %s [-i <iterations>] [-n <names>] [-p <prefix>] [-o ] [-u] [-s]\n"
+ " -i test iterations, default %d\n"
+ " -n names at each iterations, default %d\n"
+ " -p prefix for names\n"
+ " -o interlave with other dir\n"
+ " -s touch twice\n"
+ " -u mknod-unlink sequence\n"
+ " -d mkdir-chdir sequence (leaves garbage)\n",
+ argv[0], nr_iterations, nr_names);
+ return 1;
+ }
+ }
+
+
+ if (!mkdtemp(dir_name))
+ err(2, "mkdtemp");
+
+ if (chdir(dir_name))
+ err(2, "chdir");
+
+ show_dentry_state();
+
+ if (!mkdir_chdir)
+ test_inotify(".");
+
+ printf("working in temporary directory %s\n\n", dir_name);
+
+ for (iteration = 1; iteration <= nr_iterations; iteration++) {
+
+ printf("start iteration %d, %d names\n", iteration, nr_names);
+
+ tm = now();
+
+ sprintf(suffix, "%08x", iteration);
+
+ for (index = 0; index < nr_names; index++) {
+ sprintf(suffix + 8, "%08x", index);
+
+ if (mknod_unlink) {
+ if (mknod(name, S_IFREG, 0))
+ err(2, "mknod %s", name);
+ if (unlink(name))
+ err(2, "unlink %s", name);
+ } else if (mkdir_chdir) {
+ if (mkdir(name, 0775))
+ err(2, "mkdir %s", name);
+ if (chdir(name))
+ err(2, "chdir %s", name);
+ } else
+ access(name, 0);
+
+ if (second_access)
+ access(name, 0);
+
+ if (other_dir >= 0) {
+ faccessat(other_dir, name, 0, 0);
+ if (second_access)
+ faccessat(other_dir, name, 0, 0);
+ }
+ }
+
+ total_names += nr_names;
+
+ tm = now() - tm;
+ printf("iteration %d complete in %f seconds, total names %lld\n\n", iteration, tm, total_names);
+
+ show_dentry_state();
+
+ if (!mkdir_chdir)
+ test_inotify(".");
+ }
+
+ if (chdir(".."))
+ err(2, "chdir");
+
+ if (mkdir_chdir) {
+ printf("leave temporary directory %s\n", dir_name);
+ return 0;
+ }
+
+ printf("removing temporary directory %s\n", dir_name);
+ tm = now();
+ if (rmdir(dir_name))
+ err(2, "rmdir");
+ tm = now() - tm;
+ printf("remove complete in %f seconds\n\n", tm);
+
+ show_dentry_state();
+
+ return 0;
+}