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b=RGbboJgunzM0KHm8H6chrz5i1XcZ+MQ/E1LW7YG/JkKgmCiTdsjlF30PlGO4e8/7aCKaX2LMAXL+31CLpDPV4DLW0jq5VQjYZEyjNjLCk8XwOdZjUseE6OY/xeT3/XQP6lFoLbCnTLjCwTM/W/U7UXbvuFJ/2Krq6NMAkpocEqs= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from PH7PR12MB5805.namprd12.prod.outlook.com (2603:10b6:510:1d1::13) by CY8PR12MB7660.namprd12.prod.outlook.com (2603:10b6:930:84::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8792.39; Wed, 11 Jun 2025 07:56:05 +0000 Received: from PH7PR12MB5805.namprd12.prod.outlook.com ([fe80::11c7:4914:62f4:f4a3]) by PH7PR12MB5805.namprd12.prod.outlook.com ([fe80::11c7:4914:62f4:f4a3%4]) with mapi id 15.20.8792.034; Wed, 11 Jun 2025 07:56:04 +0000 Message-ID: Date: Wed, 11 Jun 2025 13:25:55 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm: Drain PCP during direct reclaim To: Wupeng Ma , akpm@linux-foundation.org, vbabka@suse.cz Cc: surenb@google.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, wangkefeng.wang@huawei.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Nikhil Dhama , "Huang, Ying" , "Rao, Bharata Bhasker" References: <20250606065930.3535912-1-mawupeng1@huawei.com> Content-Language: en-US From: Raghavendra K T In-Reply-To: <20250606065930.3535912-1-mawupeng1@huawei.com> Content-Type: text/plain; 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This > occurs because: > 1. Hugepage allocations don't actively trigger PCP draining > 2. Direct reclaim path fails to trigger drain_all_pages() when: > a) All zone pages are free/hugetlb (!did_some_progress) > b) Compaction skips due to costly order watermarks (COMPACT_SKIPPED) > > Reproduction: > - Alloc page and free the page via put_page to release to pcp > - Observe hugepage reservation failure > > Solution: > Actively drain PCP during direct reclaim for memory allocations. > This increases page allocation success rate by making stranded pages > available to any order allocations. > > Verification: > This issue can be reproduce easily in zone movable with the following > step: > > w/o this patch > # numactl -m 2 dd if=/dev/urandom of=/dev/shm/testfile bs=4k count=64 > # rm -f /dev/shm/testfile > # sync > # echo 3 > /proc/sys/vm/drop_caches > # echo 2048 > /sys/devices/system/node/node2/hugepages/hugepages-2048kB/nr_hugepages > # cat /sys/devices/system/node/node2/hugepages/hugepages-2048kB/nr_hugepages > 2029 > > w/ this patch > # numactl -m 2 dd if=/dev/urandom of=/dev/shm/testfile bs=4k count=64 > # rm -f /dev/shm/testfile > # sync > # echo 3 > /proc/sys/vm/drop_caches > # echo 2048 > /sys/devices/system/node/node2/hugepages/hugepages-2048kB/nr_hugepages > # cat /sys/devices/system/node/node2/hugepages/hugepages-2048kB/nr_hugepages > 2047 > Hello Wupeng Ma, Can you also post results of iperf/netperf for this patch in future? Thanks and Regards - Raghu