linux-kernel - Re: [PATCH v2 2/2] mm/show_mem: Add trylock while printing alloc info

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Message-ID: <2c9d2e2f-adab-4bd6-a03e-a327a4c5d6fe@suse.cz>
Date: Wed, 3 Sep 2025 11:22:05 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Yueyang Pan <pyyjason@...il.com>, Suren Baghdasaryan <surenb@...gle.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Michal Hocko <mhocko@...e.com>,
 Brendan Jackman <jackmanb@...gle.com>, Johannes Weiner <hannes@...xchg.org>,
 Zi Yan <ziy@...dia.com>, Vishal Moola <vishal.moola@...il.com>,
 Shakeel Butt <shakeel.butt@...ux.dev>, Usama Arif <usamaarif642@...il.com>
Cc: linux-mm@...ck.org, kernel-team@...a.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] mm/show_mem: Add trylock while printing alloc info

On 9/2/25 17:57, Yueyang Pan wrote:
> In production, show_mem() can be called concurrently from two
> different entities, for example one from oom_kill_process()
> another from __alloc_pages_slowpath from another kthread. This
> patch adds a spinlock and invokes trylock before printing out the
> kernel alloc info in show_mem(). This way two alloc info won't
> interleave with each other, which then makes parsing easier.
> 
> Signed-off-by: Yueyang Pan <pyyjason@...il.com>

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

> ---
>  mm/show_mem.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/show_mem.c b/mm/show_mem.c
> index 51892ce2efc4..4c876ea2b66f 100644
> --- a/mm/show_mem.c
> +++ b/mm/show_mem.c
> @@ -396,6 +396,7 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_z
>  
>  void __show_mem(unsigned int filter, nodemask_t *nodemask, int max_zone_idx)
>  {
> +	static DEFINE_SPINLOCK(mem_alloc_profiling_spinlock);
>  	unsigned long total = 0, reserved = 0, highmem = 0;
>  	struct zone *zone;
>  
> @@ -421,7 +422,7 @@ void __show_mem(unsigned int filter, nodemask_t *nodemask, int max_zone_idx)
>  	printk("%lu pages hwpoisoned\n", atomic_long_read(&num_poisoned_pages));
>  #endif
>  #ifdef CONFIG_MEM_ALLOC_PROFILING
> -	{
> +	if (spin_trylock(&mem_alloc_profiling_spinlock)) {
>  		struct codetag_bytes tags[10];
>  		size_t i, nr;
>  
> @@ -449,6 +450,7 @@ void __show_mem(unsigned int filter, nodemask_t *nodemask, int max_zone_idx)
>  						  ct->lineno, ct->function);
>  			}
>  		}
> +		spin_unlock(&mem_alloc_profiling_spinlock);
>  	}
>  #endif
>  }