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 C714D431A31 for ; Fri, 7 Aug 2026 11:29:51 +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=1786102193; cv=none; b=UezUwASGumkysq861A0pRlXd5L641df3Mgbishh9wZHG44QLeIIZ6OD6wKHQWdvhuVrm1KvTmoTItoo5565FZTeVhRg3PE+JwazBX7oLxwgdQqR6t6G7Ax+ulDnU0oM30hm7SJrM78pocMaKcF5k8wcAQNRP605MXVNbmIl0BAM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786102193; c=relaxed/simple; bh=+f3WlHQdrVoW8TMgmnNVs3vNBErFuQNLB3Jdsujwvjo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=n+7ht8+eTGDocODp57j9dWaKsZtWDARy+5e+zzVfNkaZU6pxhrMtmHclpiqdCpjuYXQplrys+hOP7uezB1UND5VfFB5cZ9SAA+T5J6dQBDoX64UfPG9232fvmLOJ3VxWJg08JnVtO8ok/CCPxTa5aYpvdE1LVgKXPESSVSc29Bc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b6YnebtQ; 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="b6YnebtQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 46B691F00A3A; Fri, 7 Aug 2026 11:29:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786102191; bh=XBZmvRMqQHFLdTL3oxi1yCZMaVS+T4GmULQiB/TUHxk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=b6YnebtQgQXjeauox18EDtK9KO+KIpY5eiEieWcczMSB3Mr++/J/NT8771qX2vpR3 rcDxljc8SL91HNA66n/mrMohOKUDbiIyokoyJjxpkZwPOIx/+oOF3+O7VZ5mA/hHtf e7RtKoxpmnRpsYjblRar1wk3KiX9oKRYwewQc20361JVlK26sg3zPgNlcA5oAZOsdg y+Y4hmgAWFhsES7XzG3IfpOvO6nFMkRzYDr/eDxFmlGcvp1e85auBOhuQNk1rCxxx2 BO9kFs5zaMIKyhjFpUXighrsVYMNWazfE3V0Cmlt+NlANqqnawRQJ5w83e4Sgda8sP 1alwcS4Y5IGog== Message-ID: <0b02ef3e-363f-4b49-a208-54cdfea56c75@kernel.org> Date: Fri, 7 Aug 2026 13:29:46 +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> <2cbd42e1-b5bb-474c-b0e7-ce3f46541891@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: 8bit On 8/6/26 11:52, Liu, Yuan1 wrote: >> -----Original Message----- >> From: David Hildenbrand (Arm) >> Sent: Thursday, August 6, 2026 4:46 PM >> 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 >> Subject: Re: [PATCH v6 1/2] mm/memory_hotplug: optimize zone contiguous >> check when changing pfn range >> >> >>> >>> Will do. >>> >>> >>> 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? > > We never account beyond the zone range, because `sub_start` and > `sub_end` are still clamped to the zone boundaries after the > alignment. > > The subsection alignment is needed for hole PFNs between memblocks > within the zone. These hole PFNs are valid for > `pfn_to_online_page()`, because they sit in a subsection that has > memory, so the whole subsection's memmap is online. > > |----------- zone range -----------| > > +-----------+---------+------------+ > + memblock 1| hole | memblock 2 | > +-----------+---------+------------+ > ^ > | > | > subsection boundary Right, but init_unavailable_range() can just return how many were actually initalized? Why can't we piggy-back on that? I think we had something similar previously, why can't we use that? We know the zone span, so we can just account all the mmap in the zone span that we initialize. What is the problem with that? -- Cheers, David