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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 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 X-Rspamd-Queue-Id: 13EFB80010 X-Stat-Signature: 1eayjmtgx6jdxeq8kg87gw9iqurc6woe X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1776158664-390189 X-HE-Meta: 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 dCKgNk4N 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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