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X-CSE-ConnectionGUID: KytF3EmwQgGs5MO9eAEJRg== X-CSE-MsgGUID: iDVahfzbSWaaDOV+ZQlKZA== X-IronPort-AV: E=McAfee;i="6800,10657,11904"; a="101239027" X-IronPort-AV: E=Sophos;i="6.27,102,1787036400"; d="scan'208";a="101239027" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Sep 2026 00:26:04 -0700 X-CSE-ConnectionGUID: dQwj5KD7RCejXc61B7nuQA== X-CSE-MsgGUID: d5aPZLlTRTaxm5Oak84Now== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,102,1787036400"; d="scan'208";a="269937740" Received: from spr10.sh.intel.com (HELO localhost) ([10.239.23.75]) by fmviesa008.fm.intel.com with ESMTP; 14 Sep 2026 00:26:01 -0700 From: Yuan Liu To: David Hildenbrand , Oscar Salvador , Mike Rapoport , Wei Yang Cc: linux-mm@kvack.org, Nanhai Zou , Chen Zhang , Yuan Liu , Jason Zeng , Chen Yu , Pan Deng , Tianyou Li , linux-kernel@vger.kernel.org Subject: [PATCH v9 0/2] mm/memory_hotplug: optimize zone contiguous check when changing pfn range Date: Mon, 14 Sep 2026 03:29:27 -0400 Message-ID: <20260914072929.1883794-1-yuan1.liu@intel.com> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 6BE6040008 X-Stat-Signature: m7ym1mnegsgknr97fnmm3ohqirw957br X-HE-Tag: 1789370765-719436 X-HE-Meta: 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 gFQNyGqO P5rJCs3JsDKzrg8ViYQAcKlcHyMAzpMFZvoKCsr/ZOxHU69pWlfOjU7S5maz+J7GykHcpolaUVyETB4HJcvISHhA72G9xTTSIh3kQ9udDlkQEpgJ68w+n+q/UFhLTDtHC6JeOCXZMmJZnT4Cvgp5aClbxBBP1gHmDCXP8y5mC10t+EMO/sbHchILhfSoztWgtoMmmXlQv79FKyVZgU4zPdBg44iBIMR89+xPiuDr1kzJ2BWJJc2qMZx4FB4I5QQ1wqpN28oUmmzt6O+YnB3zNF2ZM4ZMJE4zwoX76jQb73JcLCDhDcqD0UlXJzaiJ/zffEQaV Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This series introduces a pages_with_online_memmap member into struct zone to avoid pageblock-by-pageblock scans across the entire zone and improve memory hotplug performance. Approach ======== 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(). For hotplugged memory, pages_with_online_memmap is updated through adjust_present_page_count(), which is called during memory online and offline operations. When spanned_pages == pages_with_online_memmap, every PFN in the zone span has a valid memmap entry, so pfn_to_page() can be called for any PFN within the zone span without an additional pfn_valid() check. The counter may temporarily undercount when pages with an online memory map exist outside the current zone span. This can only happen during boot, when initializing the memory map of pages that do not fall into any zone span. Growing the zone to cover such pages and later shrinking it back may result in a value that is too small. This is safe, as it merely prevents detecting a contiguous zone. The contiguity check using pages_with_online_memmap is stricter than the old pageblock-by-pageblock scan. The old set_zone_contiguous() iterated at pageblock granularity via pageblock_pfn_to_page(), so a zone could be marked contiguous even if a subsection-sized hole existed within a pageblock. The new check requires spanned_pages == pages_with_online_memmap, meaning every PFN in the zone span must satisfy pfn_to_online_page(). Performance =========== 1. For VM hotplug performance data, please refer to Patch 2. 2. This series also benefits CXL hotplug. Performance results are as follows https://lore.kernel.org/all/20260409023552.GA2807@AE/ Tested cases ============ 1. Hotplug/unplug correctness with both online_movable and online policies, including partial unplug, middle-block offline gaps, and edge-block span shrink. 2. Large scale (256G/512G) plug/unplug performance. 3. Boot-time subsection holes (aligned/unaligned, in-zone and cross-zone) with correct pages_with_online_memmap accounting. 4. kernelcore=mirror: verified no overcounting. Patch overview ============== Patch 1 makes shrink_zone_span() more robust when memory/hole boundary falls within a subsection. It checks the full subsection range to avoid incorrectly shrinking the zone span during memory unplug. Patch 2 introduces pages_with_online_memmap to replace pageblock-by-pageblock scans across the entire zone for zone contiguity checks. v9 changes: 1. Rebased onto v7.3-rc2. 2. No code changes; refined the commit message and comments for clarity. v8: https://lore.kernel.org/linux-mm/20260901052950.3284540-1-yuan1.liu@intel.com/ v7: https://lore.kernel.org/linux-mm/20260818085702.3395529-1-yuan1.liu@intel.com/ v6: https://lore.kernel.org/linux-mm/20260723084946.189392-1-yuan1.liu@intel.com/ v5: https://lore.kernel.org/linux-mm/20260520093457.3719960-1-yuan1.liu@intel.com/ v4: https://lore.kernel.org/linux-mm/20260421125508.2317429-1-yuan1.liu@intel.com/ v3: https://lore.kernel.org/linux-mm/20260408031615.1831922-1-yuan1.liu@intel.com/ v2: https://lore.kernel.org/all/20260401070155.1420929-1-yuan1.liu@intel.com/ v1: https://lore.kernel.org/all/20260319095622.1130380-1-yuan1.liu@intel.com/ David Hildenbrand (Arm) (1): mm/memory_hotplug: make shrink_zone_span() more robust Yuan Liu (1): mm/memory_hotplug: optimize zone contiguous check when changing pfn range Documentation/mm/physical_memory.rst | 6 +++ drivers/base/memory.c | 7 ++- include/linux/mmzone.h | 69 +++++++++++++++++++++++++++ mm/memory_hotplug.c | 71 ++++++++++------------------ mm/mm_init.c | 63 +++++++++++++----------- mm/mm_init.h | 6 --- mm/page_alloc.h | 2 +- 7 files changed, 143 insertions(+), 81 deletions(-) base-commit: df2908090cda368b01ff43709f51890076c56157 -- 2.47.3