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Date: Thu, 4 Sep 2025 18:00:22 +0100
From: Catalin Marinas <catalin.marinas@arm.com>
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: Will Deacon <will@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>,
	Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
	Yang Shi <yang@os.amperecomputing.com>,
	Ard Biesheuvel <ardb@kernel.org>, Dev Jain <dev.jain@arm.com>,
	scott@os.amperecomputing.com, cl@gentwo.org,
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH v7 6/6] arm64: mm: Optimize linear_map_split_to_ptes()
Message-ID: <aLnFpndf-XikPPFf@arm.com>
References: <20250829115250.2395585-1-ryan.roberts@arm.com>
 <20250829115250.2395585-7-ryan.roberts@arm.com>
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In-Reply-To: <20250829115250.2395585-7-ryan.roberts@arm.com>

On Fri, Aug 29, 2025 at 12:52:47PM +0100, Ryan Roberts wrote:
> When splitting kernel leaf mappings, either via
> split_kernel_leaf_mapping_locked() or linear_map_split_to_ptes(),
> previously a leaf mapping was always split to the next size down. e.g.
> pud -> contpmd -> pmd -> contpte -> pte. But for
> linear_map_split_to_ptes() we can avoid the contpmd and contpte states
> because we know we want to split all the way down to ptes.
> 
> This avoids visiting all the ptes in a table if it was created by
> splitting a pmd, which is noticible on systems with a lot of memory.
> 
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>