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Mon, 3 Mar 2025 20:10:44 +0800 Message-ID: <0dbf68f3-ddb6-ecc4-bd8c-3e2c3925e761@huawei.com> Date: Mon, 3 Mar 2025 20:10:44 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH] mm/hugetlb: fix surplus pages in dissolve_free_huge_page() To: David Hildenbrand , , , CC: , , References: <20250303060920.2886263-1-tujinjiang@huawei.com> <114987e9-a449-4cc7-b897-b5b00a3cf445@redhat.com> <21afe09a-8f79-45ad-1b23-7fcb67218ea2@huawei.com> <15add3ed-8b0e-4d12-8c91-225bb23df828@redhat.com> From: Jinjiang Tu In-Reply-To: <15add3ed-8b0e-4d12-8c91-225bb23df828@redhat.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.13] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemo200002.china.huawei.com (7.202.195.209) X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 12E851C001A X-Stat-Signature: p75ppmkbh96grj3mpreye3rtokux9sj9 X-HE-Tag: 1741003851-353600 X-HE-Meta: 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 2zgVHT/b o5xAYoHhU8mNoEpoNgIZj8k582EStipzHhhs0V1QFZoGGVjO6M3x1dl3e08Wlp+zZr4hYnJKdBGqrov+uv7DsPviiBffjC1Gg+RtW6mgvZQosnzz3Dopu8E/Z+03MG4MyExEPTXOhpcBQNa/q/8c0X9LOWu8QRiOmw/KipZBptlmkxCCJkoTGOoV60qpDV49c4R5Z8217EMK4Bgg= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2025/3/3 19:47, David Hildenbrand 写道: > On 03.03.25 12:23, Jinjiang Tu wrote: >> >> 在 2025/3/3 19:16, Jinjiang Tu 写道: >>> >>> 在 2025/3/3 18:25, David Hildenbrand 写道: >>>> On 03.03.25 07:09, Jinjiang Tu wrote: >>>>> In dissolve_free_huge_page(), free huge pages are dissolved without >>>>> adjusting surplus count. However, free huge pages may be accounted as >>>>> surplus pages, and will lead to wrong surplus count. >>>>> >>>>> Steps to reproduce: >>>>> 1) create 64 huge pages for node1 >>>>> 2) run a program to reserve (don't consume) all the huge pages >>>>> 3) echo 0 > nr_huge_pages for node1. After this step, free huge >>>>> pages in >>>>> Node1 are surplus. >>>>> 4) create 80 huge pages for node0 >>>>> 5) offline memory of node1 and kill the program in step 2) >>>> >>>> Can you elaborate the "offline memory" part? How much are you >>>> offlining (the complete node vs a single memory block?) >>> I reproduce this issue on qemu. The memory onlining and offlining >>> operations are: >>> >>> 1）Node1 is memory-less at first. Hot-add memory to node1 by executing >>> the two commands in qemu monitor >>> object_add memory-backend-ram,id=mem1,size=1G >>> device_add pc-dimm,id=dimm1,memdev=mem1,node=1 >>> >>> 2）online one memory block of Node1 with： >>> echo online_movable > /sys/devices/system/node/node1/memoryX/state >>> >>> 3) offline the memory block of Node1 with： >>> echo offline > /sys/devices/system/node/node1/memoryX/state >> The memory range to offline contains the free surplus huge pages created >> in step1) ~ step3) > > Okay, that makes it a lot clearer. Can you make that clearer in the > patch description? Sure, I will send a v2 patch later. > > The problem appears when memory offlining stumbles over a free hugetlb > folio. We'll call > dissolve_free_hugetlb_folios()->dissolve_free_hugetlb_folio() to > dissolve it, but don't adjust accounting with surplus pages properly. > > I'll note that there is another dissolve_free_hugetlb_folio() caller > in the memory-failure path that might similarly be affected. >