tools/vm/page_owner_sort: support for sorting by task command name

When viewing page owner information, we may also need to the block to be
sorted by task command name.  Therefore, the following adjustments are
made:

1. Add a member variable to record task command name of block.

2. Add a new -n option to sort the information of blocks by task command
   name.

3. Add -n option explanation in the document.

Link: https://lkml.kernel.org/r/20220306030640.43054-2-yejiajian2018@email.szu.edu.cn
Signed-off-by: Jiajian Ye <yejiajian2018@email.szu.edu.cn>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Sean Anderson <seanga2@gmail.com>
Cc: Yixuan Cao <caoyixuan2019@email.szu.edu.cn>
Cc: Zhenliang Wei <weizhenliang@huawei.com>
Cc: <zhaochongxi2019@email.szu.edu.cn>
Cc: <hanshenghong2019@email.szu.edu.cn>
Cc: <zhangyinan2019@email.szu.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/vm/page_owner.rst

@@ -117,6 +117,7 @@ Usage
 		-m		Sort by total memory.
 		-p		Sort by pid.
 		-P		Sort by tgid.
+		-n		Sort by task command name.
 		-r		Sort by memory release time.
 		-s		Sort by stack trace.
 		-t		Sort by times (default).

tools/vm/page_owner_sort.c

@@ -24,6 +24,7 @@
 
 struct block_list {
 	char *txt;
+	char *comm; // task command name
 	char *stacktrace;
 	__u64 ts_nsec;
 	__u64 free_ts_nsec;
@@ -37,6 +38,7 @@ struct block_list {
 static regex_t order_pattern;
 static regex_t pid_pattern;
 static regex_t tgid_pattern;
+static regex_t comm_pattern;
 static regex_t ts_nsec_pattern;
 static regex_t free_ts_nsec_pattern;
 static struct block_list *list;
@@ -102,6 +104,13 @@ static int compare_tgid(const void *p1, const void *p2)
 	return l1->tgid - l2->tgid;
 }
 
+static int compare_comm(const void *p1, const void *p2)
+{
+	const struct block_list *l1 = p1, *l2 = p2;
+
+	return strcmp(l1->comm, l2->comm);
+}
+
 static int compare_ts(const void *p1, const void *p2)
 {
 	const struct block_list *l1 = p1, *l2 = p2;
@@ -145,6 +154,7 @@ static void check_regcomp(regex_t *pattern, const char *regex)
 }
 
 # define FIELD_BUFF 25
+# define TASK_COMM_LEN 16
 
 static int get_page_num(char *buf)
 {
@@ -233,6 +243,22 @@ static __u64 get_free_ts_nsec(char *buf)
 	return free_ts_nsec;
 }
 
+static char *get_comm(char *buf)
+{
+	char *comm_str = malloc(TASK_COMM_LEN);
+
+	memset(comm_str, 0, TASK_COMM_LEN);
+
+	search_pattern(&comm_pattern, comm_str, buf);
+	errno = 0;
+	if (errno != 0) {
+		printf("wrong comm in follow buf:\n%s\n", buf);
+		return NULL;
+	}
+
+	return comm_str;
+}
+
 static void add_list(char *buf, int len)
 {
 	if (list_size != 0 &&
@@ -266,6 +292,7 @@ static void add_list(char *buf, int len)
 		list[list_size].stacktrace++;
 	list[list_size].pid = get_pid(buf);
 	list[list_size].tgid = get_tgid(buf);
+	list[list_size].comm = get_comm(buf);
 	list[list_size].ts_nsec = get_ts_nsec(buf);
 	list_size++;
 	if (list_size % 1000 == 0) {
@@ -284,6 +311,7 @@ static void usage(void)
 		"-t	Sort by times (default).\n"
 		"-p	Sort by pid.\n"
 		"-P	Sort by tgid.\n"
+		"-n	Sort by task command name.\n"
 		"-a	Sort by memory allocate time.\n"
 		"-r	Sort by memory release time.\n"
 		"-c	Cull by comparing stacktrace instead of total block.\n"
@@ -300,7 +328,7 @@ int main(int argc, char **argv)
 	struct stat st;
 	int opt;
 
-	while ((opt = getopt(argc, argv, "acfmprstP")) != -1)
+	while ((opt = getopt(argc, argv, "acfmnprstP")) != -1)
 		switch (opt) {
 		case 'a':
 			cmp = compare_ts;
@@ -329,6 +357,9 @@ int main(int argc, char **argv)
 		case 'P':
 			cmp = compare_tgid;
 			break;
+		case 'n':
+			cmp = compare_comm;
+			break;
 		default:
 			usage();
 			exit(1);
@@ -350,6 +381,7 @@ int main(int argc, char **argv)
 	check_regcomp(&order_pattern, "order\\s*([0-9]*),");
 	check_regcomp(&pid_pattern, "pid\\s*([0-9]*),");
 	check_regcomp(&tgid_pattern, "tgid\\s*([0-9]*) ");
+	check_regcomp(&comm_pattern, "tgid\\s*[0-9]*\\s*\\((.*)\\),\\s*ts");
 	check_regcomp(&ts_nsec_pattern, "ts\\s*([0-9]*)\\s*ns,");
 	check_regcomp(&free_ts_nsec_pattern, "free_ts\\s*([0-9]*)\\s*ns");
 	fstat(fileno(fin), &st);
@@ -408,6 +440,7 @@ int main(int argc, char **argv)
 	regfree(&order_pattern);
 	regfree(&pid_pattern);
 	regfree(&tgid_pattern);
+	regfree(&comm_pattern);
 	regfree(&ts_nsec_pattern);
 	regfree(&free_ts_nsec_pattern);
 	return 0;