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 E40C2330D2A for ; Tue, 14 Apr 2026 09:24:23 +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=1776158664; cv=none; b=Jq/z4bsz1ZWndB5Bjv3NI+EGTSk3C8B6FT5+Td5xptVpXcZVbtWYm/Q2DLfJFG47y/j7jK0oN/7FRpBquz1oUyn7Are1Q31AFF76OikjUW2Tt6OWNtTpk/nVCXmEZ9c0Pz1QHMoAty74WPEip9z3Lik11ckjDjjToRDrAtZcOXQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776158664; c=relaxed/simple; bh=8DmHQNhpWGOp+HH6UU6CLgoA3IZAxo/XcUuDqTaH/10=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=MhmxRi8eOY82xYDLeL8IX9SL+5Ot2PlYCxobGb7mUK0WM6rj79jmrDXVPFjtYq2VJyeR9dFA2W6zchwznIeKQSduk/2TC7H+THfRhs3WyCGnqb3C8YrbbTREdtj+yfYBoVI4/74WlvdaOj7w9Mo0dREbuRnZOaRAEjh4WriL+JM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YKmY5FLy; 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="YKmY5FLy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 51A4EC19425; Tue, 14 Apr 2026 09:24:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776158663; bh=8DmHQNhpWGOp+HH6UU6CLgoA3IZAxo/XcUuDqTaH/10=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=YKmY5FLyGD22/qTK22QYVkokEJ3M/JMZR6NJSI8sVU+uPu3UYAzN+jfgWHgjhW1fZ GtT+zwrhGFCDyxzs/lJ0uIpoOjdpVKZpvbTgZ9b8M9l4N5MdY0vbVriY69TktdjpPO QOSJ/fYiQNOBPRSRAXSm9WnCdgXLP5HdZYeineSu9MYfOdDgM3lPZ8JMVv5OWFEACF KXIpu+vgjL8WSD/lqGLxgh/WoYu0PlpKJqDJ5h6AX7yheInWslVACjmZgkl8hlDu4X QzwqavVXJUrQFvx7Xt+GFywTVHB9PmCMsVxNORAfKM98v0R4lwCqkbACA5F1hfzXMl NO0UrYVVIQslA== Message-ID: <12b8ba83-54b1-454e-b787-2d2e967c9b58@kernel.org> Date: Tue, 14 Apr 2026 11:24:17 +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/memory hotplug/unplug: Optimize zone contiguous check when changing pfn range To: "Liu, Yuan1" , Mike Rapoport Cc: Oscar Salvador , Wei Yang , "linux-mm@kvack.org" , "Hu, Yong" , "Zou, Nanhai" , Tim Chen , "Zhuo, Qiuxu" , "Chen, Yu C" , "Deng, Pan" , "Li, Tianyou" , Chen Zhang , "linux-kernel@vger.kernel.org" References: <20260408031615.1831922-1-yuan1.liu@intel.com> <17b821b6-0176-43d5-92f7-fe2a0c4f70cf@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 4/14/26 09:06, Liu, Yuan1 wrote: >> -----Original Message----- >> From: David Hildenbrand (Arm) >> Sent: Thursday, April 9, 2026 11:08 PM >> To: Mike Rapoport >> Cc: Liu, Yuan1 ; Oscar Salvador ; >> Wei Yang ; linux-mm@kvack.org; Hu, Yong >> ; Zou, Nanhai ; Tim Chen >> ; Zhuo, Qiuxu ; Chen, Yu >> C ; Deng, Pan ; Li, Tianyou >> ; Chen Zhang ; linux- >> kernel@vger.kernel.org >> Subject: Re: [PATCH v3] mm/memory hotplug/unplug: Optimize zone contiguous >> check when changing pfn range >> >> On 4/9/26 16:40, Mike Rapoport wrote: >> a >> pageblock >> cost >> of >> present >> further >> towards >> prevents >> the >> --+ >> Reduction | >> --+ >> | >> --+ >> | >> --+ >> --+ >> Reduction | >> --+ >> | >> --+ >> | >> --+ >> \ >> of >> hotplugged >> long *pfn) >> last >> spfn, >> long spfn, >> ranges\n", >> zone *zone, >>> >>> Yeah, this looks better :) >>> >>> sashiko had several comments >>> https://sashiko.dev/#/patchset/20260408031615.1831922-1- >> yuan1.liu%40intel.com >>> >>> I skipped the ones related to hotplug, but in the mm_init part the >> comment >>> about zones that can have overlapping physical spans when mirrored >>> kernelcore is enabled seems valid. > > Hi David & Mike > > I’ve spent some time working through these issues to better understand them. > For the overlapping physical spans(mirrored kernelcore), should I avoid counting > overlap_memmap_init in memmap_init_range in the next version? > For example, change it as follows: > > +unsigned long __meminit > +memmap_init_range(unsigned long size, int nid, unsigned long zone, > + unsigned long start_pfn, > + unsigned long zone_end_pfn, > enum meminit_context context, > struct vmem_altmap *altmap, int migratetype, > bool isolate_pageblock) > { > unsigned long pfn, end_pfn = start_pfn + size; > + unsigned long nr_init = 0; > struct page *page; > > if (highest_memmap_pfn < end_pfn - 1) > @@ -893,7 +897,7 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone > if (zone == ZONE_DEVICE) { > if (!altmap) > - return; > + return 0; > > if (start_pfn == altmap->base_pfn) > start_pfn += altmap->reserve; > @@ -911,6 +915,7 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone > if (defer_init(nid, pfn, zone_end_pfn)) { > deferred_struct_pages = true; > + nr_init += end_pfn - pfn; It's confusing. Could the remaining range also include overlapping inits? Maybe the whole "skip overlapping init" should actually be handled on a higher level? I guess we'd want to skip any memblock_is_mirror(r) regions entirely. @Mike? > break; > } > } > @@ -935,8 +940,10 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone > cond_resched(); > } > + nr_init++; > pfn++; > } > + return nr_init; > } > > @ -954,13 +962,21 @@ static void __init memmap_init_zone_range(struct zone *zone, > if (start_pfn >= end_pfn) > return; > + nr_pages = memmap_init_range(end_pfn - start_pfn, nid, zone_id, > + start_pfn, zone_end_pfn, MEMINIT_EARLY, > + NULL, MIGRATE_MOVABLE, false); > + zone->pages_with_online_memmap += nr_pages; > + > >> The set_zone_contiguous/clear_zone_contiguous can be ignored I think. >> >> The comment about shrink_zone_span() is likely not realistic. >> shrink_zone_span() would not shrink over boot holes. >> >> Well, unless we have an odd case where the hole+memory starts in the >> middle of a "PAGES_PER_SUBSECTION". That would already be problematic if >> memory starts/ends in the middle of a PAGES_PER_SUBSECTION chunk. I >> don't such a case exists. >> >> We could improve shrink_zone_span() to let >> find_smallest_section_pfn/find_biggest_section_pfn test the pfn_to_nid() >> and page_zone() not on;y on the smallest/highest pfn, but also on the >> highest/smallest PFN in a PAGES_PER_SUBSECTION chunk. >> >> No need to test pfn_to_online_page() twice, as that is the same result >> for all pages in a PAGES_PER_SUBSECTION chunk. > > Hi David > > I think I understand your point. > Just to confirm, should the improvement to shrink_zone_span be included in this patch? I would do it in a separate patch that you move before this patch. -- Cheers, David