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Subject[PATCH 3/3] mm,page_owner: Filter out stacks by a threshold counter
Date
We want to be able to filter out the output on a threshold basis,
in this way we can get rid of a lot of noise and focus only on those
stacks which have an allegedly high counter.

We can control the threshold value by a new file called
'page_owner_threshold', which is 0 by default.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
include/linux/stackdepot.h | 3 +-
lib/stackdepot.c | 6 ++--
mm/page_owner.c | 61 +++++++++++++++++++++++++++++++++++++-
3 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index 20f62039f23a..ee66be40a152 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -26,7 +26,8 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
stack_action_t action);
void stack_depot_dec_count(depot_stack_handle_t handle);
int stack_depot_print_stacks_threshold(char *buf, size_t size, loff_t *pos,
- unsigned long *last_stack);
+ unsigned long *last_stack,
+ unsigned long threshold);

/*
* Every user of stack depot has to call stack_depot_init() during its own init
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 3090ae0f3958..b4a04f09a7b7 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -528,7 +528,8 @@ depot_stack_handle_t stack_depot_save_action(unsigned long *entries,
EXPORT_SYMBOL_GPL(stack_depot_save_action);

int stack_depot_print_stacks_threshold(char *buf, size_t size, loff_t *pos,
- unsigned long *last_stack)
+ unsigned long *last_stack,
+ unsigned long threshold)
{
struct stack_record *stack = NULL, *last;
struct stack_record **stacks;
@@ -547,7 +548,8 @@ int stack_depot_print_stacks_threshold(char *buf, size_t size, loff_t *pos,
for (; stack; stack = stack->next) {
if (!stack->size || stack->size < 0 ||
stack->size > size || stack->handle.valid != 1 ||
- refcount_read(&stack->count) < 1)
+ refcount_read(&stack->count) < 1 ||
+ refcount_read(&stack->count) < threshold)
continue;

ret += stack_trace_snprint(buf, size, stack->entries, stack->size, 0);
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 8c67c7eb2451..ef10cf44aaec 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -44,6 +44,7 @@ static depot_stack_handle_t early_handle;
static void init_early_allocated_pages(void);

static unsigned long last_stack = 0;
+static unsigned long threshold_count = 0;

static int __init early_page_owner_param(char *buf)
{
@@ -676,7 +677,8 @@ static ssize_t read_page_owner_stacks(struct file *file, char __user *buf,
if (!kbuf)
return ENOMEM;

- ret += stack_depot_print_stacks_threshold(kbuf, count, pos, &last_stack);
+ ret += stack_depot_print_stacks_threshold(kbuf, count, pos, &last_stack,
+ threshold_count);
if (copy_to_user(buf, kbuf, ret))
ret = -EFAULT;

@@ -687,6 +689,61 @@ static ssize_t read_page_owner_stacks(struct file *file, char __user *buf,
return ret;
}

+static ssize_t read_page_owner_threshold(struct file *file, char __user *buf,
+ size_t count, loff_t *pos)
+{
+ char *kbuf;
+ int ret = 0;
+
+ count = min_t(size_t, count, PAGE_SIZE);
+
+ if (*pos >= count)
+ return 0;
+
+ kbuf = kmalloc(count, GFP_KERNEL);
+ if (!kbuf)
+ return ENOMEM;
+
+ ret = scnprintf(kbuf, count, "%lu\n", threshold_count);
+ if (copy_to_user(buf, kbuf, ret))
+ ret = -EFAULT;
+
+ *pos += count;
+ kfree(kbuf);
+
+ return ret;
+}
+
+static ssize_t write_page_owner_threshold(struct file *file, const char __user *buf,
+ size_t count, loff_t *pos)
+{
+ char *kbuf;
+ int ret = 0;
+
+ count = min_t(size_t, count, PAGE_SIZE);
+ kbuf = kmalloc(count, GFP_KERNEL);
+ if (!kbuf)
+ return -ENOMEM;
+
+ if (copy_from_user(kbuf, buf, count)) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ kbuf[count - 1] = '\0';
+
+ ret = kstrtoul(kbuf, 10, &threshold_count);
+
+out:
+ kfree(kbuf);
+ return ret ? ret : count;
+}
+
+static const struct file_operations proc_page_owner_threshold = {
+ .read = read_page_owner_threshold,
+ .write = write_page_owner_threshold,
+};
+
static const struct file_operations proc_page_owner_stacks = {
.read = read_page_owner_stacks,
};
@@ -706,6 +763,8 @@ static int __init pageowner_init(void)
&proc_page_owner_operations);
debugfs_create_file("page_owner_stacks", 0400, NULL, NULL,
&proc_page_owner_stacks);
+ debugfs_create_file("page_owner_threshold", 0600, NULL, NULL,
+ &proc_page_owner_threshold);

return 0;
}
--
2.35.3
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