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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vlGFX-00000009qHX-0RQK; Thu, 29 Jan 2026 00:51:07 +0000 Date: Thu, 29 Jan 2026 00:51:06 +0000 From: Matthew Wilcox To: Brian Geffon Cc: Justin Green , akpm@linux-foundation.org, linux-mm@kvack.org, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-kernel@vger.kernel.org, greenjustin@google.com, rientjes@google.com, arjunroy@google.com Subject: Re: [PATCH] mm: Refactor vma_map_pages to use vm_insert_pages Message-ID: References: <20260128225648.2938636-1-greenjustin@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A68C71C0002 X-Stat-Signature: 9b1qf3gn8zf8oxa1bmp73yxtbnk4oy7y X-Rspam-User: X-HE-Tag: 1769647870-958657 X-HE-Meta: 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 Z8d4fFmD f7SrSNIKLATE5mb8xr7D5Wc1hF60SjJeUye62WeSOUVFiD0fh4kvDT40E2OuyhJiwhAJe5AXHssFOQAw6BFdOfYg8iEuw9fd0qvEltSOMQCdqW3aQ2/uHvwdCeENY1hA9SQkmmYTh5oQpQD+YSHQBLY+A3al3bUiDsh7j9Vv6ySPe8JgoSYj8QnX9p1cZyOxpLMa24snyC+zFE60xVUoT5qSIGzsv4xsqxIHbO1/n9IlHwPQxvnvXfn7RFAdr7N0cQovxTt/Ghsfws61z1sEX7CtdbeTIUzlY4GTGmZ1n+MoWdXS/+vpJFtg+SKdg0UuoT/UgaRGMuZSBz9qC71LneBhyxizqrtrq7GLo8CANraiBNQGIrHpZkdc0cxCynoC3DmC87CS99HsIxIo075asECuJrw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jan 28, 2026 at 05:59:12PM -0500, Brian Geffon wrote: > On Wed, Jan 28, 2026 at 5:57 PM Justin Green wrote: > > > > vma_map_pages currently calls vm_insert_page on each individual page in > > the mapping, which creates significant overhead because we are > > repeatedly spinlocking. Instead, we should batch insert pages using > > vm_insert_pages, which amortizes the cost of the spinlock. > > This makes sense, I wonder why this wasn't done previously? That's always a good question, because it might reveal why this patch is a bad idea ... However in this case, it simply seems to be an oversight. __vm_map_pages() was introduced in May 2019 and then vm_insert_pages() was added in April 2020. Reviewed-by: Matthew Wilcox (Oracle)