From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Muchun Song <songmuchun@bytedance.com>,
Andrew Morton <akpm@linux-foundation.org>,
Oscar Salvador <osalvador@suse.de>
Cc: Mike Rapoport <rppt@kernel.org>,
Vlastimil Babka <vbabka@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>, Michal Hocko <mhocko@suse.com>,
David Laight <david.laight.linux@gmail.com>,
"Liam R . Howlett" <liam@infradead.org>,
Suren Baghdasaryan <surenb@google.com>,
Qi Zheng <qi.zheng@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Muchun Song <muchun.song@linux.dev>
Subject: Re: [PATCH v5 01/17] mm/sparse: relax struct mem_section size constraints
Date: Wed, 9 Sep 2026 11:33:31 +0200 [thread overview]
Message-ID: <f37fbaed-3a92-4f7b-abf0-98e30d853070@kernel.org> (raw)
In-Reply-To: <20260825084608.47437-2-songmuchun@bytedance.com>
On 8/25/26 10:45, Muchun Song wrote:
> struct mem_section is currently forced to a power-of-2 size so the
> section-to-root lookup can use a mask instead of a modulo.
>
> That requirement makes future extensions harder than necessary: adding a
> small field can require configuration-dependent padding or layout checks
> just to preserve the lookup scheme. Keep the lookup correct for any
> struct mem_section size by using a plain modulo instead.
>
> Do not leave the layout entirely unconstrained, though. Keep struct
> mem_section double-word aligned so modest size changes, such as adding
> another word-sized field on 64-bit systems, still keep a compact and
> efficient layout. If future fields grow the structure beyond that sweet
> spot, the lookup remains correct; only the exact layout efficiency
> changes.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
--
Cheers,
David
next prev parent reply other threads:[~2026-09-09 9:33 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-25 8:45 [PATCH v5 00/17] mm: Introduce section-based vmemmap optimization for HugeTLB Muchun Song
2026-08-25 8:45 ` [PATCH v5 01/17] mm/sparse: relax struct mem_section size constraints Muchun Song
2026-09-09 9:33 ` David Hildenbrand (Arm) [this message]
2026-08-25 8:45 ` [PATCH v5 02/17] mm/sparse-vmemmap: rename HVO order macros Muchun Song
2026-08-25 10:05 ` Qi Zheng
2026-08-25 8:45 ` [PATCH v5 03/17] mm/mm_init: skip initializing shared vmemmap tail pages Muchun Song
2026-08-25 9:30 ` Mike Rapoport
2026-08-25 10:15 ` Qi Zheng
2026-09-09 9:36 ` David Hildenbrand (Arm)
2026-09-09 11:30 ` Muchun Song
2026-08-25 8:45 ` [PATCH v5 04/17] mm/sparse-vmemmap: initialize shared tail vmemmap pages on allocation Muchun Song
2026-08-25 9:30 ` Mike Rapoport
2026-08-25 10:40 ` Qi Zheng
2026-09-09 9:39 ` David Hildenbrand (Arm)
2026-09-09 12:49 ` Muchun Song
2026-08-25 8:45 ` [PATCH v5 05/17] mm/sparse-vmemmap: support section-based vmemmap accounting Muchun Song
2026-08-25 10:47 ` Qi Zheng
2026-08-25 8:45 ` [PATCH v5 06/17] mm/mm_init: factor out pfn_to_zone() Muchun Song
2026-08-25 10:51 ` Qi Zheng
2026-08-25 8:45 ` [PATCH v5 07/17] mm/sparse-vmemmap: move helpers ahead of future callers Muchun Song
2026-08-25 10:54 ` Qi Zheng
2026-08-25 8:45 ` [PATCH v5 08/17] mm/sparse-vmemmap: support section-based vmemmap optimization Muchun Song
2026-08-25 9:30 ` Mike Rapoport
2026-08-25 12:38 ` Qi Zheng
2026-08-25 8:46 ` [PATCH v5 09/17] mm/sparse: initialize memory sections earlier Muchun Song
2026-08-25 12:49 ` Qi Zheng
2026-09-09 9:56 ` David Hildenbrand (Arm)
2026-09-09 12:29 ` Muchun Song
2026-09-09 12:48 ` David Hildenbrand (Arm)
2026-09-09 12:58 ` Muchun Song
2026-08-25 8:46 ` [PATCH v5 10/17] mm/hugetlb: switch HugeTLB to section-based vmemmap optimization Muchun Song
2026-08-25 13:12 ` Qi Zheng
2026-08-26 2:38 ` Muchun Song
2026-08-26 3:24 ` Qi Zheng
2026-09-09 9:58 ` David Hildenbrand (Arm)
2026-09-09 13:08 ` Muchun Song
2026-09-09 13:39 ` David Hildenbrand (Arm)
2026-08-25 8:46 ` [PATCH v5 11/17] mm/sparse-vmemmap: remove SPARSEMEM_VMEMMAP_PREINIT support Muchun Song
2026-08-25 13:16 ` Qi Zheng
2026-09-09 9:59 ` David Hildenbrand (Arm)
2026-08-25 8:46 ` [PATCH v5 12/17] mm/sparse: inline usemap allocation into sparse_init_nid() Muchun Song
2026-09-09 10:01 ` David Hildenbrand (Arm)
2026-08-25 8:46 ` [PATCH v5 13/17] mm/sparse: remove section_map_size() Muchun Song
2026-09-09 10:02 ` David Hildenbrand (Arm)
2026-08-25 8:46 ` [PATCH v5 14/17] mm/hugetlb: remove HUGE_BOOTMEM_HVO Muchun Song
2026-08-25 13:28 ` Qi Zheng
2026-08-25 8:46 ` [PATCH v5 15/17] mm/hugetlb: remove HUGE_BOOTMEM_CMA Muchun Song
2026-08-25 13:42 ` Qi Zheng
2026-08-25 8:46 ` [PATCH v5 16/17] mm/hugetlb: localize struct huge_bootmem_page Muchun Song
2026-08-25 13:38 ` Qi Zheng
2026-08-25 8:46 ` [PATCH v5 17/17] mm/hugetlb: localize HUGE_BOOTMEM_ZONES_VALID Muchun Song
2026-08-25 13:40 ` Qi Zheng
2026-08-28 4:20 ` [PATCH v5 00/17] mm: Introduce section-based vmemmap optimization for HugeTLB Andrew Morton
2026-09-09 9:31 ` David Hildenbrand (Arm)
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