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 E9CA03F5BC3 for ; Tue, 15 Sep 2026 15:20:13 +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=1789485615; cv=none; b=VXC1pejdC1jBL86WnpugAFNn4L/2ChE33isaop4JkVk3L8RTh9lhAib+lBSFYGNSCqc3X85OqzeOAiVaHFkH2fjgOGTIZl57Fk8ifmNJufe4oL2G7VlWNaXE+Sq0SQKBiy7oF7U2Xhme4RHlqiZZhSnrXMDcdX5yQiBBvXxfFzM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789485615; c=relaxed/simple; bh=iwCEGl7v3IaVbA4btwfl30wlAtBpjQPpGtCyJvp46y0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=iLriNCHpm2Jw375/ujQq4c4R8Rj+l/+P1es3ElwJbNx6gBNGWMsB66bUZ8YQS+u5W8x7tSjzBmHwA4nn1e1/tguEqsE+o9/lhbTLVzKZZg4JU6VCRidR1wXdEYcFihHK0vuNj9owOkIZZIeq0yMjxaQqKLdSoD5YHfPWHGCrpLA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=F5KCAvfz; 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="F5KCAvfz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 876C51F000FF; Tue, 15 Sep 2026 15:20:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789485613; bh=isskOEQfc9nzpx03clYSswsA678FF85KNCAnq2sLlf0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=F5KCAvfzKIMU4RBO8DimZQ+dYMQ4Kck5NXykD8YT6qRLs+1XhXMqwpDa/0PF4bDCx oapOUpXIapYpujnnnHerFsH/Leztqw8ke5xgeGMOlaQ3IjWTmXOZlUimaUnfpfHigi HvdGCt9N1CGdHEvP5jvc/KMiqb2Vcf6vArbviDyRQBo0e5TJItJhNua0+a2MR7m1Qw FjzrOzP4Wx6QPyISluhoMdOwD6TW8DoBjXOc/IsvUXNpxNJXY9i35/nc13CToUYrlq vhLoq4vztd5Jk2663lqxxjJA6AE5j32XeCloFoGA5TuLQxaLqHTlhAaMg8JAoVTiOy iI+P8x/YBg68w== Message-ID: <209de483-a9a5-4d98-bda4-7998e8fdc7da@kernel.org> Date: Tue, 15 Sep 2026 17:20:07 +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 v9 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: <20260914072929.1883794-1-yuan1.liu@intel.com> <20260914072929.1883794-3-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 9/15/26 08:03, Mike Rapoport wrote: > Hi, > > On Mon, Sep 14, 2026 at 03:29:29AM -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. >> >> diff --git a/mm/mm_init.c b/mm/mm_init.c >> index 1533aebafb68..d40a8ff23370 100644 >> --- a/mm/mm_init.c >> +++ b/mm/mm_init.c >> @@ -817,22 +817,39 @@ void __meminit init_deferred_page(unsigned long pfn, int nid) >> * zone/node above the hole except for the trailing pages in the last >> * section that will be appended to the zone/node below. >> */ >> -static void __init init_unavailable_range(unsigned long spfn, >> - unsigned long epfn, >> - int zone, int node) >> +static unsigned long __init init_unavailable_range(unsigned long spfn, >> + unsigned long epfn, >> + int zone, int node) >> { >> + unsigned long next_chunk_pfn __maybe_unused = spfn; >> unsigned long pfn; >> - u64 pgcnt = 0; >> + u64 online_pgcnt = 0, pgcnt = 0; >> + bool is_online = true; >> >> for_each_valid_pfn(pfn, spfn, epfn) { >> __init_single_page(pfn_to_page(pfn), pfn, zone, node); >> __SetPageReserved(pfn_to_page(pfn)); >> pgcnt++; >> + >> + /* >> + * With vmemmap, at this stage all pages in an early section >> + * have a valid memmap and are marked as online. However, only >> + * subsections in the subsection map are actually online. >> + */ > > I'm having trouble parsing this comment. Shouldn't is say that some > subsections in a section can be offline because of holes? Maybe extending that a bit we could do "With CONFIG_SPARSEMEM_VMEMMAP, early sections have a valid memmap for all PFNs and the sections are marked online. However, we might have offline subsections in such early sections, indicated by the subsection map. While we must initialize the entire valid memmap, account only the online pages according to the subsection map as online (see pfn_to_online_page())." -- Cheers, David