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SubjectRe: Strange memory leak in 2.6.x
Tobias Hennerich <Tobias@Hennerich.de> wrote:
>
> we kindly ask for some suggestions about how to trace a memory leak
> which we suspect in the linux kernel version 2.6:

Please grab 2.6.11, apply the below patch, set CONFIG_PAGE_OWNER and follow
the below instructions.



From: Alexander Nyberg <alexn@dsv.su.se>

Introduces CONFIG_PAGE OWNER that keeps track of the call chain under which
a page was allocated. Includes a user-space helper in
Documentation/page_owner.c to sort the enormous amount of output that this
may give (thanks tridge).

Information available through /proc/page_owner

x86_64 introduces some stack noise in certain call chains so for exact
output use of x86 && CONFIG_FRAME_POINTER is suggested. Tested on x86, x86
&& CONFIG_FRAME_POINTER, x86_64

Signed-off-by: Alexander Nyberg <alexn@dsv.su.se>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/Documentation/page_owner.c | 140 +++++++++++++++++++++++++++++++++++++
25-akpm/fs/proc/proc_misc.c | 63 ++++++++++++++++
25-akpm/include/linux/mm.h | 4 +
25-akpm/lib/Kconfig.debug | 10 ++
25-akpm/mm/page_alloc.c | 56 ++++++++++++++
5 files changed, 273 insertions(+)
diff -puN /dev/null Documentation/page_owner.c
--- /dev/null 2003-09-15 06:40:47.000000000 -0700
+++ 25-akpm/Documentation/page_owner.c 2005-02-22 18:17:32.000000000 -0800
@@ -0,0 +1,140 @@
+/*
+ * User-space helper to sort the output of /proc/page_owner
+ *
+ * Example use:
+ * cat /proc/page_owner > page_owner.txt
+ * ./sort page_owner.txt sorted_page_owner.txt
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+
+struct block_list {
+ char *txt;
+ int len;
+ int num;
+};
+
+
+static struct block_list *list;
+static int list_size;
+static int max_size;
+
+struct block_list *block_head;
+
+int read_block(char *buf, FILE *fin)
+{
+ int ret = 0;
+ int hit = 0;
+ char *curr = buf;
+
+ for (;;) {
+ *curr = getc(fin);
+ if (*curr == EOF) return -1;
+
+ ret++;
+ if (*curr == '\n' && hit == 1)
+ return ret - 1;
+ else if (*curr == '\n')
+ hit = 1;
+ else
+ hit = 0;
+ curr++;
+ }
+}
+
+static int compare_txt(struct block_list *l1, struct block_list *l2)
+{
+ return strcmp(l1->txt, l2->txt);
+}
+
+static int compare_num(struct block_list *l1, struct block_list *l2)
+{
+ return l2->num - l1->num;
+}
+
+static void add_list(char *buf, int len)
+{
+ if (list_size != 0 &&
+ len == list[list_size-1].len &&
+ memcmp(buf, list[list_size-1].txt, len) == 0) {
+ list[list_size-1].num++;
+ return;
+ }
+ if (list_size == max_size) {
+ printf("max_size too small??\n");
+ exit(1);
+ }
+ list[list_size].txt = malloc(len+1);
+ list[list_size].len = len;
+ list[list_size].num = 1;
+ memcpy(list[list_size].txt, buf, len);
+ list[list_size].txt[len] = 0;
+ list_size++;
+ if (list_size % 1000 == 0) {
+ printf("loaded %d\r", list_size);
+ fflush(stdout);
+ }
+}
+
+int main(int argc, char **argv)
+{
+ FILE *fin, *fout;
+ char buf[1024];
+ int ret, i, count;
+ struct block_list *list2;
+ struct stat st;
+
+ fin = fopen(argv[1], "r");
+ fout = fopen(argv[2], "w");
+ if (!fin || !fout) {
+ printf("Usage: ./program <input> <output>\n");
+ perror("open: ");
+ exit(2);
+ }
+
+ fstat(fileno(fin), &st);
+ max_size = st.st_size / 100; /* hack ... */
+
+ list = malloc(max_size * sizeof(*list));
+
+ for(;;) {
+ ret = read_block(buf, fin);
+ if (ret < 0)
+ break;
+
+ buf[ret] = '\0';
+ add_list(buf, ret);
+ }
+
+ printf("loaded %d\n", list_size);
+
+ printf("sorting ....\n");
+
+ qsort(list, list_size, sizeof(list[0]), compare_txt);
+
+ list2 = malloc(sizeof(*list) * list_size);
+
+ printf("culling\n");
+
+ for (i=count=0;i<list_size;i++) {
+ if (count == 0 ||
+ strcmp(list2[count-1].txt, list[i].txt) != 0) {
+ list2[count++] = list[i];
+ } else {
+ list2[count-1].num += list[i].num;
+ }
+ }
+
+ qsort(list2, count, sizeof(list[0]), compare_num);
+
+ for (i=0;i<count;i++) {
+ fprintf(fout, "%d times:\n%s\n", list2[i].num, list2[i].txt);
+ }
+ return 0;
+}
diff -puN fs/proc/proc_misc.c~page-owner-tracking-leak-detector fs/proc/proc_misc.c
--- 25/fs/proc/proc_misc.c~page-owner-tracking-leak-detector 2005-02-22 18:17:32.000000000 -0800
+++ 25-akpm/fs/proc/proc_misc.c 2005-02-22 18:17:32.000000000 -0800
@@ -534,6 +534,62 @@ static struct file_operations proc_sysrq
};
#endif

+#ifdef CONFIG_PAGE_OWNER
+#include <linux/bootmem.h>
+#include <linux/kallsyms.h>
+static ssize_t
+read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+ struct page *start = pfn_to_page(min_low_pfn);
+ static struct page *page;
+ char *kbuf, *modname;
+ const char *symname;
+ int ret = 0, next_idx = 1;
+ char namebuf[128];
+ unsigned long offset = 0, symsize;
+ int i;
+
+ page = start + *ppos;
+ for (; page < pfn_to_page(max_pfn); page++) {
+ if (page->order >= 0)
+ break;
+ next_idx++;
+ continue;
+ }
+
+ if (page >= pfn_to_page(max_pfn))
+ return 0;
+
+ *ppos += next_idx;
+
+ kbuf = kmalloc(count, GFP_KERNEL);
+ if (!kbuf)
+ return -ENOMEM;
+
+ ret = snprintf(kbuf, 1024, "Page allocated via order %d\n", page->order);
+
+ for (i = 0; i < 8; i++) {
+ if (!page->trace[i])
+ break;
+ symname = kallsyms_lookup(page->trace[i], &symsize, &offset, &modname, namebuf);
+ ret += snprintf(kbuf + ret, count - ret, "[0x%lx] %s+%lu\n",
+ page->trace[i], namebuf, offset);
+ }
+
+ ret += snprintf(kbuf + ret, count -ret, "\n");
+
+ if (copy_to_user(buf, kbuf, ret))
+ ret = -EFAULT;
+
+ kfree(kbuf);
+ return ret;
+}
+
+static struct file_operations proc_page_owner_operations = {
+ .read = read_page_owner,
+};
+#endif
+
struct proc_dir_entry *proc_root_kcore;

void create_seq_entry(char *name, mode_t mode, struct file_operations *f)
@@ -612,4 +668,11 @@ void __init proc_misc_init(void)
entry->proc_fops = &ppc_htab_operations;
}
#endif
+#ifdef CONFIG_PAGE_OWNER
+ entry = create_proc_entry("page_owner", S_IWUSR | S_IRUGO, NULL);
+ if (entry) {
+ entry->proc_fops = &proc_page_owner_operations;
+ entry->size = 1024;
+ }
+#endif
}
diff -puN include/linux/mm.h~page-owner-tracking-leak-detector include/linux/mm.h
--- 25/include/linux/mm.h~page-owner-tracking-leak-detector 2005-02-22 18:17:32.000000000 -0800
+++ 25-akpm/include/linux/mm.h 2005-02-22 18:17:32.000000000 -0800
@@ -260,6 +260,10 @@ struct page {
void *virtual; /* Kernel virtual address (NULL if
not kmapped, ie. highmem) */
#endif /* WANT_PAGE_VIRTUAL */
+#ifdef CONFIG_PAGE_OWNER
+ int order;
+ unsigned long trace[8];
+#endif
};

/*
diff -puN lib/Kconfig.debug~page-owner-tracking-leak-detector lib/Kconfig.debug
--- 25/lib/Kconfig.debug~page-owner-tracking-leak-detector 2005-02-22 18:17:32.000000000 -0800
+++ 25-akpm/lib/Kconfig.debug 2005-02-22 18:17:32.000000000 -0800
@@ -167,6 +167,16 @@ config DEBUG_IOREMAP
automatically, but we'd like to make it more efficient by not
having to do that.

+config PAGE_OWNER
+ bool "Track page owner"
+ depends on DEBUG_KERNEL && X86
+ help
+ This keeps track of what call chain is the owner of a page, may
+ help to find bare alloc_page(s) leaks. Eats a fair amount of memory.
+ See Documentation/page_owner.c for user-space helper.
+
+ If unsure, say N.
+
config DEBUG_FS
bool "Debug Filesystem"
depends on DEBUG_KERNEL
diff -puN mm/page_alloc.c~page-owner-tracking-leak-detector mm/page_alloc.c
--- 25/mm/page_alloc.c~page-owner-tracking-leak-detector 2005-02-22 18:17:32.000000000 -0800
+++ 25-akpm/mm/page_alloc.c 2005-02-22 18:17:32.000000000 -0800
@@ -719,6 +719,43 @@ int zone_watermark_ok(struct zone *z, in
return 1;
}

+#ifdef CONFIG_PAGE_OWNER
+static inline int valid_stack_ptr(struct thread_info *tinfo, void *p)
+{
+ return p > (void *)tinfo &&
+ p < (void *)tinfo + THREAD_SIZE - 3;
+}
+
+static inline void __stack_trace(struct page *page, unsigned long *stack, unsigned long bp)
+{
+ int i = 0;
+ unsigned long addr;
+ struct thread_info *tinfo = (struct thread_info *)
+ ((unsigned long)stack & (~(THREAD_SIZE - 1)));
+
+ memset(page->trace, 0, sizeof(long) * 8);
+
+#ifdef CONFIG_FRAME_POINTER
+ while (valid_stack_ptr(tinfo, (void *)bp)) {
+ addr = *(unsigned long *)(bp + sizeof(long));
+ page->trace[i] = addr;
+ if (++i >= 8)
+ break;
+ bp = *(unsigned long *)bp;
+ }
+#else
+ while (valid_stack_ptr(tinfo, stack)) {
+ addr = *stack++;
+ if (__kernel_text_address(addr)) {
+ page->trace[i] = addr;
+ if (++i >= 8)
+ break;
+ }
+ }
+#endif
+}
+#endif /* CONFIG_PAGE_OWNER */
+
/*
* This is the 'heart' of the zoned buddy allocator.
*/
@@ -882,6 +919,19 @@ nopage:
}
return NULL;
got_pg:
+
+#ifdef CONFIG_PAGE_OWNER /* huga... */
+ {
+ unsigned long address, bp;
+#ifdef X86_64
+ asm ("movq %%rbp, %0" : "=r" (bp) : );
+#else
+ asm ("movl %%ebp, %0" : "=r" (bp) : );
+#endif
+ page->order = (int) order;
+ __stack_trace(page, &address, bp);
+ }
+#endif /* CONFIG_PAGE_OWNER */
zone_statistics(zonelist, z);
return page;
}
@@ -935,6 +985,9 @@ fastcall void __free_pages(struct page *
free_hot_page(page);
else
__free_pages_ok(page, order);
+#ifdef CONFIG_PAGE_OWNER
+ page->order = -1;
+#endif
}
}

@@ -1578,6 +1631,9 @@ void __init memmap_init_zone(unsigned lo
set_page_address(page, __va(start_pfn << PAGE_SHIFT));
#endif
start_pfn++;
+#ifdef CONFIG_PAGE_OWNER
+ page->order = -1;
+#endif
}
}

_
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