selftests/damon: implement a program for even-numbered memory regions access

To test schemes_tried_regions feature, we need to have a program having
specific number of regions that having different access pattern.  Existing
artificial access pattern generator, 'access_memory', cannot be used for
the purpose, since it accesses only one region at a given time.  Extending
it could be an option, but since the purpose and the implementation are
pretty simple, implementing another one from the scratch is better.

Implement such another artificial memory access program that allocates
user-defined number/size regions and accesses even-numbered regions.

Link: https://lkml.kernel.org/r/20240625180538.73134-4-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/damon/Makefile

@@ -4,7 +4,7 @@
 TEST_GEN_FILES += huge_count_read_write
 TEST_GEN_FILES += debugfs_target_ids_read_before_terminate_race
 TEST_GEN_FILES += debugfs_target_ids_pid_leak
-TEST_GEN_FILES += access_memory
+TEST_GEN_FILES += access_memory access_memory_even
 
 TEST_FILES = _chk_dependency.sh _debugfs_common.sh
 

tools/testing/selftests/damon/access_memory_even.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Artificial memory access program for testing DAMON.
+ *
+ * Receives number of regions and size of each region from user.  Allocate the
+ * regions and repeatedly access even numbered (starting from zero) regions.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+int main(int argc, char *argv[])
+{
+	char **regions;
+	clock_t start_clock;
+	int nr_regions;
+	int sz_region;
+	int access_time_ms;
+	int i;
+
+	if (argc != 3) {
+		printf("Usage: %s <number> <size (bytes)>\n", argv[0]);
+		return -1;
+	}
+
+	nr_regions = atoi(argv[1]);
+	sz_region = atoi(argv[2]);
+
+	regions = malloc(sizeof(*regions) * nr_regions);
+	for (i = 0; i < nr_regions; i++)
+		regions[i] = malloc(sz_region);
+
+	while (1) {
+		for (i = 0; i < nr_regions; i++) {
+			if (i % 2 == 0)
+				memset(regions[i], i, sz_region);
+		}
+	}
+	return 0;
+}