On 17.02.2022 16:23, Eric Dumazet wrote:
On Thu, Feb 17, 2022 at 6:05 AM Andrzej Hajda andrzej.hajda@intel.com wrote:
In cases references are taken alternately on multiple exec paths leak report can grow substantially, sorting and grouping leaks by stack_handle allows to compact it.
Signed-off-by: Andrzej Hajda andrzej.hajda@intel.com Reviewed-by: Chris Wilson chris.p.wilson@intel.com
lib/ref_tracker.c | 35 +++++++++++++++++++++++++++-------- 1 file changed, 27 insertions(+), 8 deletions(-)
diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c index 1b0c6d645d64a..0e9c7d2828ccb 100644 --- a/lib/ref_tracker.c +++ b/lib/ref_tracker.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0-or-later #include <linux/export.h> +#include <linux/list_sort.h> #include <linux/ref_tracker.h> #include <linux/slab.h> #include <linux/stacktrace.h> @@ -14,23 +15,41 @@ struct ref_tracker { depot_stack_handle_t free_stack_handle; };
+static int ref_tracker_cmp(void *priv, const struct list_head *a, const struct list_head *b) +{
const struct ref_tracker *ta = list_entry(a, const struct ref_tracker, head);const struct ref_tracker *tb = list_entry(b, const struct ref_tracker, head);return ta->alloc_stack_handle - tb->alloc_stack_handle;+}
- void __ref_tracker_dir_print(struct ref_tracker_dir *dir, unsigned int display_limit) {
unsigned int i = 0, count = 0; struct ref_tracker *tracker;
unsigned int i = 0;
depot_stack_handle_t stack; lockdep_assert_held(&dir->lock);if (list_empty(&dir->list))return;list_sort(NULL, &dir->list, ref_tracker_cmp);What is going to be the cost of sorting a list with 1,000,000 items in it ?
Do we really have such cases?
I just want to make sure we do not trade printing at most ~10 references (from netdev_wait_allrefs()) to a soft lockup :/ with no useful info if something went terribly wrong.
I suggest that you do not sort a potential big list, and instead attempt to allocate an array of @display_limits 'struct stack_counts'
I suspect @display_limits will always be kept to a reasonable value (less than 100 ?)
I though rather about 16 :) In theory everything is possible, but do we have real case examples which could lead to 100 stack traces? Maybe some frameworks used by multiple consumers (drivers) ???
struct stack_counts { depot_stack_handle_t stack_handle; unsigned int count; }
Then, iterating the list and update the array (that you can keep sorted by ->stack_handle)
Then after iterating, print the (at_most) @display_limits handles found in the temp array.
OK, could be faster and less invasive. Other solution would be keeping the array in dir and update in every tracker alloc/free, this way we avoid iteration over potentially big list, but it would cost memory and since printing is rather rare I am not sure if it is worth.
I will try your proposition.
Regards Andrzej
list_for_each_entry(tracker, &dir->list, head) {
if (i < display_limit) {pr_err("leaked reference.\n");if (tracker->alloc_stack_handle)stack_depot_print(tracker->alloc_stack_handle);i++;} else {
if (i++ >= display_limit) break;
}
if (!count++)stack = tracker->alloc_stack_handle;if (stack == tracker->alloc_stack_handle &&!list_is_last(&tracker->head, &dir->list))continue;pr_err("leaked %d references.\n", count);if (stack)stack_depot_print(stack);count = 0; }-- 2.25.1