From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 69D31279DC2 for ; Tue, 28 Apr 2026 07:06:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777359982; cv=none; b=M1uUp0CvEUXtPq6Ai0BlaUKCVtjaNYewh7fNato3DlAvRqEULKSW1dZH+YrfHPp7rKwN0HXT0wg4lI5yRkGw0ClnD7AkQylUndyE2wP/P769pv0XRGKMt6WFyE41/x0iDyVuKvS1F+FUQgONGeczpoePunQvWKuqTuuAPKkM2Z0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777359982; c=relaxed/simple; bh=WMCSp2ANSc4rzWe/QHswbhY2Nx6MR99VRyVaYQXiNX8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HwjiRjoYK57gswWaBW6PtaDf89xbq0JMBPVTK4mlrRCe1TVU7cwHAX6QuPRClF3EIb+dhaNlbV1pWT6bduWZDXg9x/4jmqAWb0JAKqCi+cogxo7976ctIve7QEA/uQiduHpk/RJyXqTd4ZMhRWBaSXdXMhK/PH39dVMVwNNK35I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aEyfOAJ0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="aEyfOAJ0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 765AAC2BCAF; Tue, 28 Apr 2026 07:06:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777359982; bh=WMCSp2ANSc4rzWe/QHswbhY2Nx6MR99VRyVaYQXiNX8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=aEyfOAJ0gD3wAl9oC0a8NTWIbaNvFiVVSppPD+t2m6hrhSKnzBmAIBcBWFxEJhM24 moMFkwtxtrLzGEFreyfwnwjsGROFT2hMMf1wFHHKybyhXCJqTMz9Ox+RPVBkeUoxHc 8ArQ8tN+CorcLAQVvwhsY2QQ3Wy+bk0kKfnEiK2L88LlOJmKHN253HUYT2HdtuVlB8 DO5WoBc+LKdxkwHVV2JEyyZsvozErLyWDK49Vd7JGTqHJziEhrw+cora0uBHW3jgO6 biWyUQ5XO9gsCKE8iMnRuQsxsdEbO9dzBOj1etJGvui47LAz/qkRaLXa5mpJZupysK qU2G9oVXQ6l2g== Message-ID: Date: Tue, 28 Apr 2026 09:06:14 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/page_alloc: replace kernel_init_pages() with batch page clearing To: "Salunke, Hrushikesh" , Andrew Morton Cc: ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rkodsara@amd.com, bharata@amd.com, ankur.a.arora@oracle.com, shivankg@amd.com References: <20260422102729.166599-1-hsalunke@amd.com> <20260423041249.156eb95889696ccfaf23dca1@linux-foundation.org> <1253ca14-69de-418f-8f94-b08e8105e924@kernel.org> 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 4/28/26 05:55, Salunke, Hrushikesh wrote: > > On 24-04-2026 14:22, David Hildenbrand (Arm) wrote: >> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding. >> >> >> On 4/24/26 10:42, Salunke, Hrushikesh wrote: >>> Hi Andrew, >>> >>> The idea was to keep it alongside clear_highpage_kasan_tagged() as its >>> batch counterpart, but currently it is only used by page_alloc.c. >> Right. >> >> Looking at init_vmalloc_pages(), I wonder if it could also benefit from batching >> if we find that pages are actually contiguous. >> >> That would require looking up multiple pages at once. vmalloc_to_pages() or sth >> like that. Surely, doing such an optimized page table walk could be beneficial >> by itself. > > Interesting idea. For the general case where we only have struct page > pointers, we'd need physical contiguity detection and a batched page > table walk as you described. But looking at init_vmalloc_pages() > specifically, it already has the vmalloc virtual address which is > contiguous, so can we just do following and potentially skip the > vmalloc_to_page() walk entirely: > > clear_pages(kasan_reset_tag((void *)start), size >> PAGE_SHIFT); > > What do you think? would this simpler approach work > , or am I missing something? Good question. :) That way you'd be operating on the vmalloc address range, not on the direct map. Is the vmalloc address range guaranteed to be writable at that point? -- Cheers, David