linux-kernel - Re: [PATCH v2] mm, slub: print CPU id (and its node) on slab OOM

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Message-ID: <2b56938d-d999-4bad-a220-491aa29ef152@suse.cz>
Date: Mon, 26 Aug 2024 20:39:56 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Axel Rasmussen <axelrasmussen@...gle.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Christoph Lameter <cl@...ux.com>,
 David Rientjes <rientjes@...gle.com>, Hyeonggon Yoo <42.hyeyoo@...il.com>,
 Joonsoo Kim <iamjoonsoo.kim@....com>, Pekka Enberg <penberg@...nel.org>,
 Roman Gushchin <roman.gushchin@...ux.dev>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2] mm, slub: print CPU id (and its node) on slab OOM

On 8/14/24 23:50, Axel Rasmussen wrote:
> Depending on how remote_node_defrag_ratio is configured, allocations can
> end up in this path as a result of the local node being OOM, despite the
> allocation overall being unconstrained (node == -1).
> 
> When we print a warning, printing the current CPU makes that situation
> more clear (i.e., you can immediately see which node's OOM status
> matters for the allocation at hand).
> 
> Acked-by: David Rientjes <rientjes@...gle.com>
> Signed-off-by: Axel Rasmussen <axelrasmussen@...gle.com>

Thanks, replaced v1 in the slab tree.

> ---
>  mm/slub.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index c9d8a2497fd6..3088260bf75d 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3416,14 +3416,15 @@ slab_out_of_memory(struct kmem_cache *s, gfp_t gfpflags, int nid)
>  {
>  	static DEFINE_RATELIMIT_STATE(slub_oom_rs, DEFAULT_RATELIMIT_INTERVAL,
>  				      DEFAULT_RATELIMIT_BURST);
> +	int cpu = raw_smp_processor_id();
>  	int node;
>  	struct kmem_cache_node *n;
>  
>  	if ((gfpflags & __GFP_NOWARN) || !__ratelimit(&slub_oom_rs))
>  		return;
>  
> -	pr_warn("SLUB: Unable to allocate memory on node %d, gfp=%#x(%pGg)\n",
> -		nid, gfpflags, &gfpflags);
> +	pr_warn("SLUB: Unable to allocate memory on CPU %u (of node %d) on node %d, gfp=%#x(%pGg)\n",
> +		cpu, cpu_to_node(cpu), nid, gfpflags, &gfpflags);
>  	pr_warn("  cache: %s, object size: %u, buffer size: %u, default order: %u, min order: %u\n",
>  		s->name, s->object_size, s->size, oo_order(s->oo),
>  		oo_order(s->min));