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From: Dave Hansen <dave.hansen@intel.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Arnd Bergmann <arnd@arndb.de>, Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Hyeonggon Yoo <42.hyeyoo@gmail.com>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	linux-mm@kvack.org, linux-sh@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH] mm/slab: Fix undefined init_cache_node_node() for NUMA and !SMP
Date: Wed, 22 Mar 2023 09:49:48 -0700	[thread overview]
Message-ID: <d0bf2342-4f1c-bf2f-b912-a4558288a3d0@intel.com> (raw)
In-Reply-To: <ZBsw9lRbJU4c2wLD@casper.infradead.org>

On 3/22/23 09:46, Matthew Wilcox wrote:
> On Wed, Mar 22, 2023 at 09:16:55AM -0700, Dave Hansen wrote:
>> On 3/21/23 09:40, Matthew Wilcox wrote:
>>> On Tue, Mar 21, 2023 at 09:30:59AM +0100, Geert Uytterhoeven wrote:
>>>> -#if (defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG)) || defined(CONFIG_SMP)
>>>> +#if defined(CONFIG_NUMA) || defined(CONFIG_SMP)
>>> I'm amused by the thought of CONFIG_NUMA without CONFIG_SMP.
>>> Is it possible to have one node with memory and a single CPU, then
>>> another node with memory and no CPU?
>> It's _possible_ for sure, just unlikely.  The most likely place these
>> days is probably a teensy tiny VM that just happens to have some
>> performance-differentiated memory exposed to it for some reason.  Maybe
>> it's got a slice of slow PMEM or fast High-Bandwidth memory for whatever
>> reason.
> Right, you can construct such a system, but do we support the CONFIG
> options of NUMA enabled and SMP disabled?  It seems so niche that we
> shouldn't be spending time testing that combination.

On x86 we don't:

> config NUMA
>         bool "NUMA Memory Allocation and Scheduler Support"
>         depends on SMP
>         depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)

... which I think is fine.  I totally agree that NUMA without SMP is too
niche to care about.  Heck, !SMP is almost too niche to care about these
days.

  reply	other threads:[~2023-03-22 16:49 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-21  8:30 [PATCH] mm/slab: Fix undefined init_cache_node_node() for NUMA and !SMP Geert Uytterhoeven
2023-03-21  8:41 ` John Paul Adrian Glaubitz
2023-03-21  8:50   ` Geert Uytterhoeven
2023-03-21 15:07     ` Vlastimil Babka
2023-03-21 15:29 ` Randy Dunlap
2023-03-21 16:40 ` Matthew Wilcox
2023-03-21 16:43   ` Randy Dunlap
2023-03-22 16:16   ` Dave Hansen
2023-03-22 16:46     ` Matthew Wilcox
2023-03-22 16:49       ` Dave Hansen [this message]
2023-03-23  8:25       ` Geert Uytterhoeven
2023-03-23  8:28         ` John Paul Adrian Glaubitz
2023-03-23  8:36           ` Geert Uytterhoeven

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