linux-kernel - Re: [PATCH] mm/page_owner.c: record task name of process

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Date:   Thu, 3 Feb 2022 16:52:30 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Yixuan Cao <caoyixuan2019@...il.szu.edu.cn>,
        akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Waiman Long <longman@...hat.com>
Subject: Re: [PATCH] mm/page_owner.c: record task name of process

On 2/3/22 13:00, Yixuan Cao wrote:
> I think in tracing page allocation behavior,
> It is useful to record the task name of the process.
> 
> Although the current Page Owner has recorded the process ID,
> When the process exits,
> It is difficult to distinguish the specific function of this process,
> This brings some inconvenience to debugging memory problems.
> 
> Therefore, add the task name information to the Page Owner,
> So that users can clearly understand the task name of the process.
> At the same time, with this information,
> We can use tools/vm/page_owner_sort.c,
> Provides more output modes for Page Owner.
> 
> Signed-off-by: Yixuan Cao <caoyixuan2019@...il.szu.edu.cn>

A patch with the same goal is already part of Waiman's series:
https://lore.kernel.org/all/20220131192308.608837-5-longman@redhat.com/

> ---
>  mm/page_owner.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 99e360df9465..a8d666cd13ac 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -29,6 +29,7 @@ struct page_owner {
>  	u64 ts_nsec;
>  	u64 free_ts_nsec;
>  	pid_t pid;
> +	char task_name[TASK_COMM_LEN];
>  };
>  
>  static bool page_owner_enabled = false;
> @@ -163,6 +164,7 @@ static inline void __set_page_owner_handle(struct page_ext *page_ext,
>  		page_owner->gfp_mask = gfp_mask;
>  		page_owner->last_migrate_reason = -1;
>  		page_owner->pid = current->pid;
> +		strcpy(page_owner->task_name, current->comm);
>  		page_owner->ts_nsec = local_clock();
>  		__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
>  		__set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
> @@ -229,6 +231,7 @@ void __folio_copy_owner(struct folio *newfolio, struct folio *old)
>  		old_page_owner->last_migrate_reason;
>  	new_page_owner->handle = old_page_owner->handle;
>  	new_page_owner->pid = old_page_owner->pid;
> +	strcpy(new_page_owner->task_name, old_page_owner->task_name);
>  	new_page_owner->ts_nsec = old_page_owner->ts_nsec;
>  	new_page_owner->free_ts_nsec = old_page_owner->ts_nsec;
>  
> @@ -339,9 +342,10 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
>  		return -ENOMEM;
>  
>  	ret = snprintf(kbuf, count,
> -			"Page allocated via order %u, mask %#x(%pGg), pid %d, ts %llu ns, free_ts %llu ns\n",
> +			"Page allocated via order %u, mask %#x(%pGg), pid %d, task_name [%s], ts %llu ns, free_ts %llu ns\n",
>  			page_owner->order, page_owner->gfp_mask,
>  			&page_owner->gfp_mask, page_owner->pid,
> +			page_owner->task_name,
>  			page_owner->ts_nsec, page_owner->free_ts_nsec);
>  
>  	if (ret >= count)
> @@ -415,9 +419,10 @@ void __dump_page_owner(const struct page *page)
>  	else
>  		pr_alert("page_owner tracks the page as freed\n");
>  
> -	pr_alert("page last allocated via order %u, migratetype %s, gfp_mask %#x(%pGg), pid %d, ts %llu, free_ts %llu\n",
> +	pr_alert("page last allocated via order %u, migratetype %s, gfp_mask %#x(%pGg), pid %d, task_name [%s], ts %llu, free_ts %llu\n",
>  		 page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask,
> -		 page_owner->pid, page_owner->ts_nsec, page_owner->free_ts_nsec);
> +		 page_owner->pid, page_owner->task_name,
> +		 page_owner->ts_nsec, page_owner->free_ts_nsec);
>  
>  	handle = READ_ONCE(page_owner->handle);
>  	if (!handle)
> @@ -629,3 +634,4 @@ static int __init pageowner_init(void)
>  	return 0;
>  }
>  late_initcall(pageowner_init)
> +