linux-kernel - Re: [PATCH mm-unstable] mm/page_owner: record single timestamp value for high order allocations

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Date:   Wed, 8 Feb 2023 18:02:48 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Mike Rapoport <rppt@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Michal Hocko <mhocko@...nel.org>,
        David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH mm-unstable] mm/page_owner: record single timestamp value
 for high order allocations

On 1/21/23 17:50, Hyeonggon Yoo wrote:
> When allocating a high-order page, separate allocation timestamp is
> recorded for each sub-page resulting in different timestamp values between
> them.
> 
> This behavior is not consistent with the behavior when recording free
> timestamp and caused confusion when analyzing memory dumps. Record single
> timestamp for the entire allocation, aligning with the behavior for
> free timestamps.
> 
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@...il.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/page_owner.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index f0553bedb39d..80dc8f4050fa 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -163,6 +163,7 @@ static inline void __set_page_owner_handle(struct page_ext *page_ext,
>  {
>  	struct page_owner *page_owner;
>  	int i;
> +	u64 ts_nsec = local_clock();
>  
>  	for (i = 0; i < (1 << order); i++) {
>  		page_owner = get_page_owner(page_ext);
> @@ -172,7 +173,7 @@ static inline void __set_page_owner_handle(struct page_ext *page_ext,
>  		page_owner->last_migrate_reason = -1;
>  		page_owner->pid = current->pid;
>  		page_owner->tgid = current->tgid;
> -		page_owner->ts_nsec = local_clock();
> +		page_owner->ts_nsec = ts_nsec;
>  		strscpy(page_owner->comm, current->comm,
>  			sizeof(page_owner->comm));
>  		__set_bit(PAGE_EXT_OWNER, &page_ext->flags);