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Date: Mon, 19 Sep 2022 17:23:23 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Oscar Salvador <osalvador@...e.de>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Michal Hocko <mhocko@...e.com>,
Eric Dumazet <edumazet@...gle.com>,
Waiman Long <longman@...hat.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Marco Elver <elver@...gle.com>,
Andrey Konovalov <andreyknvl@...il.com>,
Alexander Potapenko <glider@...gle.com>
Subject: Re: [PATCH v2 3/3] mm,page_owner: Filter out stacks by a threshold
counter
On 9/5/22 05:10, Oscar Salvador wrote:
> 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.
The name could suggest it has to do something with "page_owner" but in fact
it only affects "page_owner_stacks".
So maybe "page_owner_stacks_threshold" ? But now it's rather long. Or maybe
"page_owner_stacks_min_count" ? Also long but maybe the most self-evident?
> Signed-off-by: Oscar Salvador <osalvador@...e.de>
> ---
> include/linux/stackdepot.h | 3 ++-
> lib/stackdepot.c | 6 +++--
> mm/page_owner.c | 51 +++++++++++++++++++++++++++++++++++++-
> 3 files changed, 56 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
> index 19d3f8295df8..742038216cd0 100644
> --- a/include/linux/stackdepot.h
> +++ b/include/linux/stackdepot.h
> @@ -25,7 +25,8 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
> gfp_t gfp_flags, bool can_alloc,
> enum stack_depot_action 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);
> +int stack_depot_print_stacks_threshold(char *buf, size_t size, loff_t *pos,
> + 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 a198b2dbe3fb..a31e882853ab 100644
> --- a/lib/stackdepot.c
> +++ b/lib/stackdepot.c
> @@ -566,7 +566,8 @@ 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)
> +int stack_depot_print_stacks_threshold(char *buf, size_t size, loff_t *pos,
> + unsigned long threshold)
> {
> int i = *pos, ret = 0;
> struct stack_record **stacks, *stack;
> @@ -585,7 +586,8 @@ 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 d88e6b4aefa0..5b895d347c5f 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -43,6 +43,8 @@ static depot_stack_handle_t early_handle;
>
> static void init_early_allocated_pages(void);
>
> +static unsigned long threshold;
> +
> static int __init early_page_owner_param(char *buf)
> {
> int ret = kstrtobool(buf, &page_owner_enabled);
> @@ -675,7 +677,7 @@ 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);
> + ret += stack_depot_print_stacks_threshold(kbuf, count, pos, threshold);
> if (copy_to_user(buf, kbuf, ret))
> ret = -EFAULT;
>
> @@ -683,6 +685,51 @@ static ssize_t read_page_owner_stacks(struct file *file, char __user *buf,
> return ret;
> }
>
> +static int page_owner_threshold_show(struct seq_file *p, void *v)
> +{
> + seq_printf(p, "%lu\n", threshold);
> + return 0;
> +}
> +
> +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);
> +
> +out:
> + kfree(kbuf);
> + return ret ? ret : count;
> +}
> +
> +static int open_page_owner_threshold(struct inode *inode, struct file *file)
> +{
> + return single_open(file, page_owner_threshold_show, NULL);
> +}
> +
> +
> +static const struct file_operations proc_page_owner_threshold = {
> + .open = open_page_owner_threshold,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .write = write_page_owner_threshold,
> + .release = single_release,
> +};
> +
> static const struct file_operations proc_page_owner_stacks = {
> .read = read_page_owner_stacks,
> };
> @@ -702,6 +749,8 @@ 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;
> }
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