From: Muchun Song <muchun.song@linux.dev>
To: Qi Zheng <qi.zheng@linux.dev>
Cc: Muchun Song <songmuchun@bytedance.com>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
Mike Rapoport <rppt@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>,
Christophe Leroy <chleroy@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
"Liam R . Howlett" <liam@infradead.org>,
Vlastimil Babka <vbabka@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH 1/6] mm/sparse-vmemmap: drop VMEMMAP_POPULATE_DAX
Date: Sat, 19 Sep 2026 22:07:19 +0800 [thread overview]
Message-ID: <4AA6C66B-0FD8-49F3-8447-959A3E438FC2@linux.dev> (raw)
In-Reply-To: <186ee2ba-daf3-4120-a3e3-101cac1ff5a1@linux.dev>
> On Sep 19, 2026, at 22:01, Qi Zheng <qi.zheng@linux.dev> wrote:
> On 9/13/26 4:37 PM, Muchun Song wrote:
>> VMEMMAP_POPULATE_DAX currently distinguishes DAX vmemmap population in two
>> places: it keeps allocations on the normal path and takes a reference when
>> a backing page is supplied for reuse.
>> After Device DAX switched to the common per-zone shared tail page, both
>> conditions can be determined locally. DAX supplies ptpfn for every shared
>> tail mapping and requests an allocation only for compound head mappings,
>> whose PFNs are not optimizable. Therefore, vmemmap_optimizable_pfn() alone
>> selects the correct allocation path.
>> When ptpfn is supplied, the caller is reusing an existing backing page.
>> Once the slab allocator is available, take a reference for each reused
>
> Does the availability of slab mean the buddy allocator is already being
> used? Could there be a window where the buddy allocator is functional
> but slab hasn't become available yet?
Yes, because the slab allocator is based on buddy allocator. But I want to know
what's your concern here?
next prev parent reply other threads:[~2026-09-19 14:07 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-13 8:37 [PATCH 0/6] mm: Unify Device DAX and HugeTLB vmemmap population paths Muchun Song
2026-09-13 8:37 ` [PATCH 1/6] mm/sparse-vmemmap: drop VMEMMAP_POPULATE_DAX Muchun Song
2026-09-19 14:01 ` Qi Zheng
2026-09-19 14:07 ` Muchun Song [this message]
2026-09-21 3:43 ` Qi Zheng
2026-09-21 3:49 ` Muchun Song
2026-09-22 7:54 ` Qi Zheng
2026-09-13 8:37 ` [PATCH 2/6] mm/sparse-vmemmap: support device DAX in common vmemmap path Muchun Song
2026-09-22 8:02 ` Qi Zheng
2026-09-22 11:34 ` Muchun Song
2026-09-13 8:37 ` [PATCH 3/6] mm/sparse-vmemmap: drop Device DAX-specific population path Muchun Song
2026-09-22 8:06 ` Qi Zheng
2026-09-13 8:37 ` [PATCH 4/6] mm/sparse-vmemmap: remove the unused ptpfn argument Muchun Song
2026-09-22 8:12 ` Qi Zheng
2026-09-13 8:37 ` [PATCH 5/6] powerpc/mm: make vmemmap_populate_compound_pages() static Muchun Song
2026-09-22 8:14 ` Qi Zheng
2026-09-13 8:37 ` [PATCH 6/6] mm/sparse-vmemmap: open-code vmemmap_populate_address() Muchun Song
2026-09-22 8:18 ` Qi Zheng
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