From: Harry Yoo <harry@kernel.org>
To: Hao Li <hao.li@linux.dev>, vbabka@kernel.org
Cc: akpm@linux-foundation.org, cl@gentwo.org, rientjes@google.com,
roman.gushchin@linux.dev, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/slub: deduplicate NUMA policy calculation in allocation paths
Date: Wed, 24 Jun 2026 14:14:55 +0900 [thread overview]
Message-ID: <0c69b68d-7c67-4d3a-9f90-86a56bc229e7@kernel.org> (raw)
In-Reply-To: <20260623110952.411041-1-hao.li@linux.dev>
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On 6/23/26 8:04 PM, Hao Li wrote:
> Currently, alloc_from_pcs() and __slab_alloc_node() both calculate the
> NUMA policy independently. Since they are called consecutively in paths
> like __kmalloc_nolock_noprof() and slab_alloc_node(), this leads to
> redundant code snippets.
Right.
> Introduce a helper function to resolve the NUMA policy once, eliminating
> the duplicated code and reducing execution overhead.
Nice.
> Also remove __slab_alloc_node() function because it is almost empty.
Nice!
> The callers of __slab_alloc_node now call ___slab_alloc() directly.
>
> Additional notes:
>
> Previously, when slab_strict_numa was enabled, alloc_from_pcs() and
> __slab_alloc_node() could each resolve the task mempolicy, so
> MPOL_INTERLEAVE or MPOL_WEIGHTED_INTERLEAVE could advance the
> interleave state twice for a single object allocation attempt.
>
> With this change, the strict NUMA node is resolved once and reused by
> both alloc_from_pcs() and ___slab_alloc().
Nice catch!
> This is a behavior change, but it better matches the intent of
> selecting one policy node for one allocation attempt.
Right.
and I think backporting is unnecessary here.
> Signed-off-by: Hao Li <hao.li@linux.dev>
> ---
> Changes in v2:
> * Use a better function name apply_strict_numa_policy() (Thanks Harry)
> * Remove almost empty function __slab_alloc_node.
> * Add a local variable, strict_node, so the retry path in
> __kmalloc_nolock_noprof() computes the strict NUMA node from the original
> node parameter instead of a previously resolved node value.
What about overriding 'node' before retry label instead?
node = apply_strict_numa_policy(node);
[...]
retry:
[...]
Otherwise LGTM.
--
Cheers,
Harry / Hyeonggon
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next prev parent reply other threads:[~2026-06-24 5:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-23 11:04 [PATCH v2] mm/slub: deduplicate NUMA policy calculation in allocation paths Hao Li
2026-06-24 5:14 ` Harry Yoo [this message]
2026-06-24 8:17 ` Hao Li
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