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b=eWem/Bwmp1XCRrRsQXwUGDy4l94/ozbhmpiaCTcmkpXW1/L7mpVOUJ9gi90xWqitq JCRUj+O4pLBG5KCdDfTFIw5A6nBYFs2LWMTk5RqA+G/RbMFaGmqDzHLX+RDR+JEwTm szptenKBVF5Spv1fs634JKY5qWzjEpekC963DxJD9tVt6o8pdnbJ7Laj0ulHelQQo3 M49q38ec8DXsRKWEm13Ei/J9976cdst9nAiQjXwHETdqxcGhljvyqb+QlbDFhewoMU hoPij3qwAgmFIUO75xzIgWMug7OuyBG8wt1kM9/3bc0LDPGcy7rKL58ORJ9X6jftFJ QKLLsv61kexGA== Message-ID: <72934683-0409-4e6a-9d34-daabade131eb@kernel.org> Date: Thu, 26 Mar 2026 10:53:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory hotplug/unplug: Optimize zone contiguous check when changing pfn range To: "Chen, Yu C" , "Liu, Yuan1" , Mike Rapoport Cc: Oscar Salvador , Wei Yang , "linux-mm@kvack.org" , "Hu, Yong" , "Zou, Nanhai" , Tim Chen , "Zhuo, Qiuxu" , "Deng, Pan" , "Li, Tianyou" , Chen Zhang , "linux-kernel@vger.kernel.org" References: <20260319095622.1130380-1-yuan1.liu@intel.com> <48b497e5-1545-4376-a898-f3813a6ef989@kernel.org> <168ab3c0-c44f-4d48-b7dc-33196b7ba6a5@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-Server: rspam05 X-Rspamd-Queue-Id: 178A4180005 X-Stat-Signature: d93g33q7fatgbmd5gwanxds9mjs5oohn X-Rspam-User: X-HE-Tag: 1774518837-606442 X-HE-Meta: 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 vCUOV8r7 BxmIoZtyEtcrdt4J/Jyth/Gsgenv3p+EInwwZabrZRhAWlDpxcGfZtGFAcY45Nm4qGizl+ontPmWrqmY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/26/26 08:38, Chen, Yu C wrote: > On 3/26/2026 3:30 PM, Liu, Yuan1 wrote: >>> -----Original Message----- > > [ .... ] > >> >> Btw, can we introduce a new kernel command-line parameter to allow >> users to select >> the memory block size? This could also address the current issue. >> >> Test Results as below, memory block size 128MB Vs. 2GB >> +----------------+------+---------------+--------------+----------------+ >> |                | Size |    128MG      |    2GB       | Time Reduction | >> |                +------+---------------+--------------+----------------+ >> | Plug Memory    | 256G |      10s      |       3s     |       70%      | >> |                +------+---------------+--------------+----------------+ >> |                | 512G |      36s      |       7s     |       81%      | >> +----------------+------+---------------+--------------+----------------+ >>   +----------------+------+---------------+-------------- >> +----------------+ >> |                | Size |    128MG      |    2GB       | Time Reduction | >> |                +------+---------------+--------------+----------------+ >> | Unplug Memory  | 256G |      11s      |      3s      |       72%      | >> |                +------+---------------+--------------+----------------+ >> |                | 512G |      36s      |      7s      |       81%      | >> +----------------+------+---------------+--------------+----------------+ >> >> And I see the UV system has already this (Kernel parameter is >> uv_memblksize). >> I think if we can introduce a common kernel parameter for memory block >> size configuration? >> > > Is it possible to turn uv_memblksize into a generic commandline > memblksize without > introducing extra parameter? We don't want that, and it's kind of a workaround for the problem. :) I think we would want to only account pages towards pages_with_online_memmap that fall within the zone span. We will not account pages initialized that are outside the zone span. Growing the zone and later trying to shrink them will only possibly see a "too small" pages_with_online_memmap value. That is fine, it simply prevents detecting "contiguous" so it's safe. We can document that, and in the future we could handle it a bit nicer (e.g., indicate these pages as being just fill material). So indeed, I guess we want to teach init_unavailable_range() to only account towards zone->pages_with_online_memmap whatever falls into the zone span. That could be done internally, or from the callers by calling init_unavailable_range() once for the out-of-zone range and once for the in-zone-range. -- Cheers, David