tools/vm/page_owner_sort.c: add switch between culling by stacktrace and txt

Culling by comparing stacktrace would casue loss of some information.  For
example, if there exists 2 blocks which have the same stacktrace and the
different head info

  Page allocated via order 0, mask 0x108c48(...), pid 73696,
    ts 1578829190639010 ns, free_ts 1576583851324450 ns
    prep_new_page+0x80/0xb8
    get_page_from_freelist+0x924/0xee8
    __alloc_pages+0x138/0xc18
    alloc_pages+0x80/0xf0
    __page_cache_alloc+0x90/0xc8

  Page allocated via order 0, mask 0x108c48(...), pid 61806,
    ts 1354113726046100 ns, free_ts 1354104926841400 ns
    prep_new_page+0x80/0xb8
    get_page_from_freelist+0x924/0xee8
    __alloc_pages+0x138/0xc18
    alloc_pages+0x80/0xf0
    __page_cache_alloc+0x90/0xc8

After culling, it would be like this

  2 times, 2 pages:
  Page allocated via order 0, mask 0x108c48(...), pid 73696,
    ts 1578829190639010 ns, free_ts 1576583851324450 ns
    prep_new_page+0x80/0xb8
    get_page_from_freelist+0x924/0xee8
    __alloc_pages+0x138/0xc18
    alloc_pages+0x80/0xf0
    __page_cache_alloc+0x90/0xc8

The info of second block missed.  So, add -c to turn on culling by
stacktrace.  By default, it will cull by txt.

Link: https://lkml.kernel.org/r/20211129145658.2491-1-zhangyinan2019@email.szu.edu.cnSigned-off-by: Yinan Zhang <zhangyinan2019@email.szu.edu.cn>
Cc: Changhee Han <ch0.han@lge.com>
Cc: Sean Anderson <seanga2@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Tang Bin <tangbin@cmss.chinamobile.com>
Cc: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Cc: Zhenliang Wei <weizhenliang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/vm/page_owner_sort.c

@@ -51,6 +51,13 @@ int read_block(char *buf, int buf_size, FILE *fin)
 	return -1; /* EOF or no space left in buf. */
 }
 
+static int compare_txt(const void *p1, const void *p2)
+{
+	const struct block_list *l1 = p1, *l2 = p2;
+
+	return strcmp(l1->txt, l2->txt);
+}
+
 static int compare_stacktrace(const void *p1, const void *p2)
 {
 	const struct block_list *l1 = p1, *l2 = p2;
@@ -137,12 +144,14 @@ static void usage(void)
 		"-m	Sort by total memory.\n"
 		"-s	Sort by the stack trace.\n"
 		"-t	Sort by times (default).\n"
+		"-c	cull by comparing stacktrace instead of total block.\n"
 	);
 }
 
 int main(int argc, char **argv)
 {
 	int (*cmp)(const void *, const void *) = compare_num;
+	int cull_st = 0;
 	FILE *fin, *fout;
 	char *buf;
 	int ret, i, count;
@@ -151,7 +160,7 @@ int main(int argc, char **argv)
 	int err;
 	int opt;
 
-	while ((opt = getopt(argc, argv, "mst")) != -1)
+	while ((opt = getopt(argc, argv, "mstc")) != -1)
 		switch (opt) {
 		case 'm':
 			cmp = compare_page_num;
@@ -162,6 +171,9 @@ int main(int argc, char **argv)
 		case 't':
 			cmp = compare_num;
 			break;
+		case 'c':
+			cull_st = 1;
+			break;
 		default:
 			usage();
 			exit(1);
@@ -209,7 +221,10 @@ int main(int argc, char **argv)
 
 	printf("sorting ....\n");
 
+	if (cull_st == 1)
 		qsort(list, list_size, sizeof(list[0]), compare_stacktrace);
+	else
+		qsort(list, list_size, sizeof(list[0]), compare_txt);
 
 	list2 = malloc(sizeof(*list) * list_size);
 	if (!list2) {
@@ -219,9 +234,11 @@ int main(int argc, char **argv)
 
 	printf("culling\n");
 
+	long offset = cull_st ? &list[0].stacktrace - &list[0].txt : 0;
+
 	for (i = count = 0; i < list_size; i++) {
 		if (count == 0 ||
-		    strcmp(list2[count-1].stacktrace, list[i].stacktrace) != 0) {
+		    strcmp(*(&list2[count-1].txt+offset), *(&list[i].txt+offset)) != 0) {
 			list2[count++] = list[i];
 		} else {
 			list2[count-1].num += list[i].num;