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Date: Wed, 2 Nov 2022 13:35:04 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: "zhaoyang.huang" <zhaoyang.huang@...soc.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Zhaoyang Huang <huangzhaoyang@...il.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, ke.wang@...soc.com,
steve.kang@...soc.com, Oscar Salvador <osalvador@...e.de>,
Michal Hocko <mhocko@...e.com>
Subject: Re: [RFC PATCH] mm: introduce accounting of page_owner via backtrace
On 11/2/22 13:06, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
>
> Page_owner could be accounted and sort via its backtrace, which could
> simplify the output.
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
At first glance this looks like the same goal as Oscar's (CC'd) patchset:
https://lore.kernel.org/linux-mm/20220905031012.4450-1-osalvador@suse.de/
> ---
> include/linux/page_owner.h | 7 +++
> mm/page_owner.c | 113 +++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 120 insertions(+)
>
> diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
> index 119a0c9..c86a342 100644
> --- a/include/linux/page_owner.h
> +++ b/include/linux/page_owner.h
> @@ -3,6 +3,13 @@
> #define __LINUX_PAGE_OWNER_H
>
> #include <linux/jump_label.h>
> +#include <linux/stackdepot.h>
> +
> +struct hash_object {
> + int count;
> + depot_stack_handle_t trace_hash;
> + struct rb_node rb_node;
> +};
>
> #ifdef CONFIG_PAGE_OWNER
> extern struct static_key_false page_owner_inited;
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index e4c6f3f..3d014fd 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -42,6 +42,12 @@ struct page_owner {
> static depot_stack_handle_t early_handle;
>
> static void init_early_allocated_pages(void);
> +static void store_user_hash(depot_stack_handle_t trace_hash, int count);
> +static DEFINE_SPINLOCK(stack_hash_lock);
> +static struct hash_object ho_pool[8192];
> +static int ho_pool_free_count = ARRAY_SIZE(ho_pool);
> +struct rb_root user_hash_root = RB_ROOT;
> +
>
> static int __init early_page_owner_param(char *buf)
> {
> @@ -152,6 +158,8 @@ void __reset_page_owner(struct page *page, unsigned short order)
> page_owner->free_handle = handle;
> page_owner->free_ts_nsec = free_ts_nsec;
> page_ext = page_ext_next(page_ext);
> + if (!i)
> + store_user_hash(page_owner->handle, -(1 << order));
> }
> }
>
> @@ -190,6 +198,7 @@ noinline void __set_page_owner(struct page *page, unsigned short order,
> return;
>
> handle = save_stack(gfp_mask);
> + store_user_hash(handle, 1 << order);
> __set_page_owner_handle(page_ext, handle, order, gfp_mask);
> }
>
> @@ -570,6 +579,105 @@ void __dump_page_owner(const struct page *page)
> return 0;
> }
>
> +static void store_user_hash(depot_stack_handle_t trace_hash, int count)
> +{
> + struct rb_node *rb_parent;
> + unsigned int trace_hash_parent;
> + struct rb_node **link = &user_hash_root.rb_node;
> + struct hash_object *hash_parent = NULL;
> + struct hash_object *hash_object = NULL;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&stack_hash_lock, flags);
> + while (*link) {
> + rb_parent = *link;
> + hash_parent = rb_entry(rb_parent, struct hash_object, rb_node);
> + trace_hash_parent = hash_parent->trace_hash;
> + if (trace_hash < trace_hash_parent)
> + link = &hash_parent->rb_node.rb_left;
> + else if (trace_hash_parent < trace_hash)
> + link = &hash_parent->rb_node.rb_right;
> + else {
> + hash_object = rb_entry(*link, struct hash_object, rb_node);
> + hash_object->count += count;
> + if (!RB_EMPTY_ROOT(&user_hash_root)
> + && !hash_object->count) {
> + rb_erase(&hash_object->rb_node, &user_hash_root);
> + }
> + spin_unlock_irqrestore(&stack_hash_lock, flags);
> + return;
> + }
> + }
> + /*
> + * hash_object is the 1st node represent this trace_hash
> + * insert it to user_hash_root
> + */
> + hash_object = ho_pool_free_count ? &ho_pool[--ho_pool_free_count] : NULL;
> + if (!hash_object) {
> + spin_unlock_irqrestore(&stack_hash_lock, flags);
> + return;
> + }
> + hash_object->trace_hash = trace_hash;
> + /* add the node to rb tree*/
> + rb_link_node(&hash_object->rb_node, rb_parent, link);
> + rb_insert_color(&hash_object->rb_node, &user_hash_root);
> + spin_unlock_irqrestore(&stack_hash_lock, flags);
> + return;
> +}
> +static ssize_t print_owner_stack(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> +{
> + struct hash_object *object;
> + struct rb_node *rb;
> + unsigned long *entries;
> + unsigned int nr_entries;
> + char *kbuf;
> + int i, ret = 0;
> + unsigned long flags;
> +
> + count = min_t(size_t, count, PAGE_SIZE);
> + kbuf = kmalloc(count, GFP_KERNEL);
> + if (!kbuf)
> + return -ENOMEM;
> +
> + rb = file->private_data ? (struct rb_node *)file->private_data : rb_first(&user_hash_root);
> + if(!rb)
> + return 0;
> + spin_lock_irqsave(&stack_hash_lock, flags);
> + object = rb_entry(rb, struct hash_object, rb_node);
> + if (object) {
> + while (!object->trace_hash || object->count <= 0) {
> + rb = rb_next(rb);
> + object = rb ? rb_entry(rb, struct hash_object, rb_node) : NULL;
> + if (!object) {
> + spin_unlock_irqrestore(&stack_hash_lock, flags);
> + kfree(kbuf);
> + return 0;
> + }
> + }
> + nr_entries = stack_depot_fetch(object->trace_hash, &entries);
> + ret += snprintf(kbuf + ret, count - ret, "count %d\n", object->count);
> + if (ret >= count)
> + goto err;
> + for (i = 0; i < nr_entries; i++) {
> + void *ptr = (void *)entries[i];
> + ret += snprintf(kbuf + ret, count - ret, " [<%p>] %pS\n", ptr, ptr);
> + if (ret >= count)
> + goto err;
> + }
> + }
> + file->private_data = (void *)rb_next(rb);
> + spin_unlock_irqrestore(&stack_hash_lock, flags);
> + if (copy_to_user(buf, kbuf, ret))
> + ret = -EFAULT;
> +
> + kfree(kbuf);
> + return ret;
> +err:
> + spin_unlock_irqrestore(&stack_hash_lock, flags);
> + kfree(kbuf);
> + return -ENOMEM;
> +}
> +
> static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
> {
> unsigned long pfn = zone->zone_start_pfn;
> @@ -661,6 +769,9 @@ static void init_early_allocated_pages(void)
> static const struct file_operations proc_page_owner_operations = {
> .read = read_page_owner,
> };
> +static const struct file_operations proc_page_owner_simple_operations = {
> + .read = print_owner_stack,
> +};
>
> static int __init pageowner_init(void)
> {
> @@ -671,6 +782,8 @@ static int __init pageowner_init(void)
>
> debugfs_create_file("page_owner", 0400, NULL, NULL,
> &proc_page_owner_operations);
> + debugfs_create_file("page_owner_simple", 0400, NULL, NULL,
> + &proc_page_owner_simple_operations);
>
> return 0;
> }
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