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 C3BA3306744 for ; Wed, 19 Aug 2026 15:43:38 +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=1787154220; cv=none; b=ZXdMxC39XBBUozrWBYFEuEiOqLUHD9pH6BTfoqAs02cFubaRy8k3F4p0y9PnmKm1aTf9VsK262Kj+LCt6HTQwVre98P6jgKhKc6Go4EC3iJHyhVJUaSJsxNJ3sWlupC7PMCTpj/GmOHapRYcLcY7mkqPc5UMMCxVEvCnP1clG3I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787154220; c=relaxed/simple; bh=o/NpWT8IgYScSADLGCGlvwfeZ8U5pzgdZx9WKyTBj4o=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jKqs0bfgrUfOQvfd/Y4HgBw4AM89GYaJBc4MLUL5EM16XOMaFIiTutZ/G2iztZI/Y1Q+wR6o+aV3PdDBuJkhlsIhKpgaakshZt9P+eiqr4h/bqDIUt6imtp/OL4Mn7VHlylYXXnxf/6gIyP3phyxWqM9Rr6bPCAaaBPXSPy6Gsw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VJgTEOEc; 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="VJgTEOEc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 511971F000E9; Wed, 19 Aug 2026 15:43:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787154218; bh=38JhnhHXecQ6hRRQfHnTqEwVWVkxH6ubOJI2lsidQN0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=VJgTEOEcslv7heA9gjgAu/iGr2yaBO6vB/pN2zKgXLJhTIgm94p5S0H/kvBwGj5+q m/DYpEd/YI7DwEGcll0WxUCvGPohSWN8IuSLwPjy7SqncmGauBYgy8b2QgF+3g5UV5 KbaSZ4Fdm+DluAgWk4O8iGc3rf7giL/kRYGz0xQHvTE+tL3apP5cmXyns1WwZu8eSx QkxgEQ3gskFSf5eXEscBm5FLz/R3EGBY8oxKkEPpoSD8Tc/Tcg167y5yzbrWk14Pt8 q1RAGvhQuMoOHs1L2phIvgtKADNze9FVY14/L9nsAiJu6VK0zCs9CL21TgZanRarNw Av+Vg0Iu2QV+w== Message-ID: Date: Wed, 19 Aug 2026 17:43:31 +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 v7 2/2] mm/memory_hotplug: optimize zone contiguous check when changing pfn range To: Mike Rapoport , Yuan Liu Cc: Oscar Salvador , Wei Yang , linux-mm@kvack.org, Nanhai Zou , Chen Zhang , Jason Zeng , Chen Yu , Pan Deng , Tianyou Li , linux-kernel@vger.kernel.org References: <20260818085702.3395529-1-yuan1.liu@intel.com> <20260818085702.3395529-3-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: 7bit On 8/19/26 16:56, Mike Rapoport wrote: > On Tue, Aug 18, 2026 at 04:57:02AM -0400, Yuan Liu wrote: >> When move_pfn_range_to_zone() or remove_pfn_range_from_zone() updates a >> zone, set_zone_contiguous() rescans the entire zone pageblock-by-pageblock >> to rebuild zone->contiguous. For large zones this is a significant cost >> during memory hotplug and hot-unplug. >> >> Add a new zone member, pages_with_online_memmap, that tracks the >> number of pages within the zone span that have an online memory map, >> including present pages and memory holes whose memory map has been >> initialized and for which pfn_to_online_page() succeeds. >> >> For early boot memory, pages_with_online_memmap is calculated in >> memmap_init_zone_range(). PFNs initialized by memmap_init_range() are >> included in pages_with_online_memmap, and hole PFNs for which >> pfn_to_online_page() succeeds are also counted in >> init_unavailable_range(). > > In what scenario it is possible that pfn_to_online_page() would fail at > that point? pfn_to_online_page()==false even though pfn_valid()==true in case we have a subsection-sized hole in an early section. -- Cheers, David