From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 549BC41E6A6 for ; Thu, 6 Aug 2026 08:45:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786005943; cv=none; b=aDcV+AqF1HuxQOciBthQrrNxLxYa3QAn7ynGuywlL57967xNVb/VXhDX7S1OmxHjqs5FAhFJ4L4c0pQSjnfzCHRE1GNLl/UVetn6zc7QruEEJmifhDhyNiwz97aA1mp7lIxhsce0xoB8Q3OT2jpjAoWV+Rk4pkiWWuvKhtJUioc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786005943; c=relaxed/simple; bh=TcWDEuHGOTGOAIR3jb63+q+w6KYdYxYFEjJ82/Rgw1Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=l4cvvf8umBkWCN2K1Ic1vYvHGH5uWRyVzd9OffyYR0LAJ3eMgm8bLEEkcDTZARbnpJJBir4KSgvK8CtFYbVMYRaOAbGS+R4heAAbequ7x0181XoPEeg/2qpbtcu0aYjsPHl87gD5/H1CPCWYS98RybZTPnoyhRr9LA5o0OSPrPM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jVDnwyuV; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jVDnwyuV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A78CE1F000E9; Thu, 6 Aug 2026 08:45:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786005941; bh=lbr9b/qtPOe/Faxe4tR1mMwAtMEUx9LiVSdAIQLniKM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=jVDnwyuVrbu8xmITUkewRJXdiCkGi85k5+li2u7HyhGmXFfz4BbFRkDNfIpL9WDUE qlumkyj9GRy1Veh3uHqgNq7tR11Wo/u3XjPYkfzgxfUtNu0bnAiV6iW//9ag6tvjKp TlVD6Cc+Wp9RFTvCWcKfBTsqC+A2BDLHrJAqfWtlU5qspp8st7bIyUYhqAW4ocpYkv Ov+DIl+0w0ZJRyZViZbYl1GTB5pm0tWNipd2etEMHnoI7Hn7qT7Itdq0ydoIfAsjYe ywiicx4HXX1lfD/IPg2IPGHEAFxgXJhYzgBeJvhpKNNtosjydaGxeo8ID0D/n3LV2g nVMFd4bckyYGQ== Message-ID: <2cbd42e1-b5bb-474c-b0e7-ce3f46541891@kernel.org> Date: Thu, 6 Aug 2026 10:45:36 +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 v6 1/2] mm/memory_hotplug: optimize zone contiguous check when changing pfn range To: "Liu, Yuan1" , Oscar Salvador , Mike Rapoport , Wei Yang Cc: "linux-mm@kvack.org" , "Zou, Nanhai" , "Deng, Pan" , "Li, Tianyou" , Chen Zhang , "Zeng, Jason" , "linux-kernel@vger.kernel.org" References: <20260723084946.189392-1-yuan1.liu@intel.com> <20260723084946.189392-2-yuan1.liu@intel.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit >>> +static void __init update_zone_online_memmap_pages(struct zone *zone, >>> + unsigned long start_pfn, >>> + unsigned long end_pfn, >>> + unsigned long *hole_pfn) >>> +{ >>> +#ifdef CONFIG_SPARSEMEM_VMEMMAP >>> + unsigned long zone_start_pfn = zone->zone_start_pfn; >>> + unsigned long zone_end_pfn = zone_start_pfn + zone->spanned_pages; >> >> These two can be const. > > Will do. > >>> + unsigned long sub_start, sub_end; >>> + >>> + sub_start = max(ALIGN_DOWN(start_pfn, PAGES_PER_SUBSECTION), >>> + zone_start_pfn); >>> + sub_end = min(ALIGN(end_pfn, PAGES_PER_SUBSECTION), zone_end_pfn); >> >> Hm, I don't immediately understand why we do the PAGES_PER_SUBSECTION >> thing >> here. Why is that required? > > pages_with_online_memmap counts all PFNs where pfn_to_online_page() is > valid. With CONFIG_SPARSEMEM_VMEMMAP, pfn_section_valid() operates at > PAGES_PER_SUBSECTION granularity — when any page in a subsection has > memory, the entire subsection is valid/online. So we align to subsection > boundaries to include hole pages within partially-populated subsections. But we must never account exceeding the zone range. So I don't understand why we would have to care about PAGES_PER_SUBSECTION here at all? -- Cheers, David