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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Sn2dg4v4; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B0C7460A2601 for ; Wed, 11 Nov 2026 08:00:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Sn2dg4v4 Received: by smtp.kernel.org (Postfix) with ESMTPSA id F41D01F00A05; Wed, 11 Nov 2026 08:00:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794384019; bh=ymCWphKfzcDfO41n1HV0rigfpNtNxqnMt90FaYWdvh4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Sn2dg4v4Q0NRYHhHk+EwkVrva7WTpJ32iIZNPLtwX1VLgiGQBCCGLp0Zhu9zujEWE O5c2LSjMzcr3UYvSWrmtB4Xl0D2lyGYnmaW6FSo1BqDProO/Btm+A+vd/BC+yB/5YI 9n2YNd6kDO4tw4z4Wka8ipOEHsO5eQ3nSlenDf2ahQYdSM+d1yfEoVaqSd7nwP5Y4/ MpLJkqgV1lL+ZCMYYBJCkDnpEVTqpTpH4EziTtVs2YSJ/4K8chde5xh862ZTfUJt6m 04y/ZZP1WO3VkuWy/+YJvWdmfVHJYPQR9jjbVk7NECFd9tmphdmGouCexMKKPWXnA2 gawIpNy0TiUqw== Message-ID: <5f9c449e-43b3-4732-9c14-8199418cace0@kernel.org> Date: Wed, 11 Nov 2026 09:00:10 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/migrate: improve mlock tracking for PTE-mapped large folios To: Wandun Chen , hughd@google.com, akpm@linux-foundation.org Cc: ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kiryl Shutsemau References: <20261110123218.1579490-1-chenwandun1@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/10/26 13:32, Wandun Chen wrote: > From: Wandun Chen > > Commit ab521b4142aa ("mm/rmap: improve mlock tracking for large folios") > mlocks a large folio when all its pages are added in one rmap operation. > However, when a PTE-mapped large folio is migrated, remove_migration_pte() > restores PTEs individually, passing nr_pages = 1 to the rmap helpers. As a > result, PG_mlocked is not set on the destination folio. > > Reclaim can restore mlock in try_to_unmap(), but Mlocked in /proc/meminfo > remains undercounted until that scan occurs. > > Restore mlock once the full mapping has been restored in a locked VMA > under one page table lock, rather than waiting for try_to_unmap() to > restore the mlock state. > > Signed-off-by: Wandun Chen > --- > mm/migrate.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 94033c222e04..140e291d4587 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -353,6 +353,7 @@ static bool remove_migration_pte(struct folio *folio, > { > struct rmap_walk_arg *rmap_walk_arg = arg; > DEFINE_FOLIO_VMA_WALK(pvmw, rmap_walk_arg->folio, vma, addr, PVMW_SYNC | PVMW_MIGRATION); > + unsigned long nr_ptes = 0; > > while (page_vma_mapped_walk(&pvmw)) { > rmap_t rmap_flags = RMAP_NONE; > @@ -446,9 +447,16 @@ static bool remove_migration_pte(struct folio *folio, > else > folio_add_file_rmap_pte(folio, new, vma); > set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); > + > + nr_ptes++; > } > - if (READ_ONCE(vma->vm_flags) & VM_LOCKED) > + if (READ_ONCE(vma->vm_flags) & VM_LOCKED) { > + if (folio_test_large(folio) && > + nr_ptes == folio_nr_pages(folio) && > + !(pvmw.flags & PVMW_PGTABLE_CROSSED)) > + mlock_vma_folio(folio, vma); > mlock_drain_local(); > + } > > trace_remove_migration_pte(pvmw.address, pte_val(pte), > compound_order(new)); I guess pte batching would be one way of handling it, but that requires more churn. The spirit is similar as in try_to_unmap_one(), where we count the number of ptes in one VMA. For consistency, I would call it "ptes". @Kiryl, can you take a look? BTW, why don't we care about that in try_to_migrate? -- Cheers, David