[001/114] tools/vm/page_owner_sort.c: sort by stacktrace before culling

Commit Message

Andrew Morton March 25, 2022, 1:08 a.m. UTC

From: Sean Anderson <[e-mail]>
Subject: tools/vm/page_owner_sort.c: sort by stacktrace before culling

The contents of page_owner have changed to include more information than
the stack trace.  On a modern kernel, the blocks look like

Page allocated via order 0, mask 0x0(), pid 1, ts 165564237 ns, free_ts 0 ns
 register_early_stack+0x4b/0x90
 init_page_owner+0x39/0x250
 kernel_init_freeable+0x11e/0x242
 kernel_init+0x16/0x130

Sorting by the contents of .txt will result in almost no repeated pages,
as the pid, ts, and free_ts will almost never be the same.  Instead, sort
by the contents of the stack trace, which we assume to be whatever is
after the first line.

[[e-mail]: fix NULL-pointer dereference when comparing stack traces]
  Link: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Sean Anderson <[e-mail]>
Signed-off-by: Sean Anderson <[e-mail]>
Cc: Changhee Han <[e-mail]>
Cc: Tang Bin <[e-mail]>
Cc: Zhang Shengju <[e-mail]>
Cc: Zhenliang Wei <[e-mail]>
Cc: Stephen Rothwell <[e-mail]>
Cc: Yinan Zhang <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 tools/vm/page_owner_sort.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

Patch

--- a/tools/vm/page_owner_sort.c~tools-vm-page_owner_sortc-sort-by-stacktrace-before-culling
+++ a/tools/vm/page_owner_sort.c
@@ -23,6 +23,7 @@ 
 
 struct block_list {
 	char *txt;
+	char *stacktrace;
 	int len;
 	int num;
 	int page_num;
@@ -51,11 +52,11 @@  int read_block(char *buf, int buf_size,
 	return -1; /* EOF or no space left in buf. */
 }
 
-static int compare_txt(const void *p1, const void *p2)
+static int compare_stacktrace(const void *p1, const void *p2)
 {
 	const struct block_list *l1 = p1, *l2 = p2;
 
-	return strcmp(l1->txt, l2->txt);
+	return strcmp(l1->stacktrace, l2->stacktrace);
 }
 
 static int compare_num(const void *p1, const void *p2)
@@ -121,6 +122,7 @@  static void add_list(char *buf, int len)
 	list[list_size].page_num = get_page_num(buf);
 	memcpy(list[list_size].txt, buf, len);
 	list[list_size].txt[len] = 0;
+	list[list_size].stacktrace = strchr(list[list_size].txt, '\n') ?: "";
 	list_size++;
 	if (list_size % 1000 == 0) {
 		printf("loaded %d\r", list_size);
@@ -199,7 +201,7 @@  int main(int argc, char **argv)
 
 	printf("sorting ....\n");
 
-	qsort(list, list_size, sizeof(list[0]), compare_txt);
+	qsort(list, list_size, sizeof(list[0]), compare_stacktrace);
 
 	list2 = malloc(sizeof(*list) * list_size);
 	if (!list2) {
@@ -211,7 +213,7 @@  int main(int argc, char **argv)
 
 	for (i = count = 0; i < list_size; i++) {
 		if (count == 0 ||
-		    strcmp(list2[count-1].txt, list[i].txt) != 0) {
+		    strcmp(list2[count-1].stacktrace, list[i].stacktrace) != 0) {
 			list2[count++] = list[i];
 		} else {
 			list2[count-1].num += list[i].num;