From: Pedro Falcato <pfalcato@suse.de>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org,
riel@surriel.com, liam@infradead.org, vbabka@kernel.org,
harry@kernel.org, jannh@google.com, lance.yang@linux.dev,
qi.zheng@linux.dev, ayushr@modal.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: synchronize with PTE table reclaim for all folio sizes
Date: Thu, 5 Nov 2026 11:37:45 +0000 [thread overview]
Message-ID: <auxqWxUfRVvxnk_n@pedro-suse.tail5790ac.ts.net> (raw)
In-Reply-To: <affd6da4e8d0de1424a4e0b3bafcd1324dfb6c97.1793847060.git.baolin.wang@linux.alibaba.com>
On Thu, Nov 05, 2026 at 10:56:28AM +0800, Baolin Wang wrote:
> Similar to commit 243cf1f67b36 ("mm: memory: fix truncation removing mapped
> folios"), the '!pmd_present()' check in page_vma_mapped_walk() can also race
> with concurrent page table reclamation via zap_empty_pte_table().
>
> page_vma_mapped_walk() is used by many functions including try_to_unmap(),
> try_to_migrate(), folio_mkclean(), pfn_mkclean_range(), remove_migration_ptes(),
> page_mapped_in_vma(), and mapping_wrprotect_range(). Except for try_to_unmap()
> and try_to_migrate(), the other callers do not perform post-walk accounting
> checks, so the race has no observable impact on them.
>
> For migration, the race can cause unnecessary retries. For reclaim via
> try_to_unmap(), the race can cause failure to reclaim a folio that is in
> fact already unmapped (as shown below), which may lead to unexpected OOM
> or increased refaults.
This is very handwavy. Do you have numbers? Does this actually make sense?
--
Pedro
prev parent reply other threads:[~2026-11-05 11:37 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-05 2:56 Baolin Wang
2026-11-05 3:22 ` Qi Zheng
2026-11-05 4:54 ` Lance Yang
2026-11-05 5:48 ` Lance Yang
2026-11-05 9:00 ` Baolin Wang
2026-11-05 10:06 ` David Hildenbrand (Arm)
2026-11-05 11:18 ` Baolin Wang
2026-11-05 13:22 ` Lance Yang
2026-11-05 11:37 ` Pedro Falcato [this message]
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