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.

[seanga2@gmail.com: fix NULL-pointer dereference when comparing stack traces]
Link: https://lkml.kernel.org/r/20211125162653.1855958-1-seanga2@gmail.com
Link: https://lkml.kernel.org/r/20211124193709.1805776-1-seanga2@gmail.com
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Cc: Changhee Han <ch0.han@lge.com>
Cc: Tang Bin <tangbin@cmss.chinamobile.com>
Cc: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Cc: Zhenliang Wei <weizhenliang@huawei.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Yinan Zhang <zhangyinan2019@email.szu.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/tools/vm/page_owner_sort.c b/tools/vm/page_owner_sort.c
index 9ebb84a..5582d84 100644 (file)
--- a/tools/vm/page_owner_sort.c
+++ b/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, FILE *fin)
        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;