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Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by CY6PEPF0000004C.mail.protection.outlook.com (10.167.247.137) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.569.4 via Frontend Transport; Thu, 29 Oct 2026 04:16:51 +0000 Received: from satlexmb08.amd.com (10.181.42.217) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.53; Wed, 28 Oct 2026 23:16:50 -0500 Received: from [192.168.0.152] (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.53 via Frontend Transport; Wed, 28 Oct 2026 23:16:45 -0500 Message-ID: Date: Thu, 29 Oct 2026 09:46:44 +0530 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] sched/numa: make free-space tiering promotion bypass configurable To: Li Zhe , , , , , , , , , , , , , , , , , CC: , , References: <20261028041253.74839-1-lizhe.67@bytedance.com> <20261028041253.74839-2-lizhe.67@bytedance.com> Content-Language: en-US From: Bharata B Rao In-Reply-To: <20261028041253.74839-2-lizhe.67@bytedance.com> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: oqVkSRXzBFedJKBR+kLSwCEO1vxosnB0uJwkaHQJM9bJ9+Ys9ZXtC09C7juq/0fh44zti7Z9EJUh+gLSOYpzrRyVSjBzFYmlkF/xW+X4YLHHmNUbWdKA931UtCJvKcJ0GxkgVq6lqzvk0jURkKKkTnnaP7et3qF4HHdPCxFfF85MJdy4+NWtmAUSVbJqjpxdof4xAxZezMYU9lskPpDiTfIsyYQi4aGEezs/78V9NWle2bj1oA9fC++8pdpEtKuyd/SNxPRBewnty4OZjCRTLv2WU41ImOwF350CMO2Xkb4pIsoO8sexHwqgjCsobS7PBB2ZBsZy4gJWUKeupsgVtau8PeDTjgQPExrwU5542kxl/cTwRVFFsHpWi8dqAstuLzYUjKztuaOx6ljAx0lGBZzIM2N7OCtB2d8wzgWzOuaED0OY8XCLvoBK5sm9Xztl X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Oct 2026 04:16:51.4189 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0fbb6a21-1bb4-419a-37f5-08df35737548 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CY6PEPF0000004C.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB7130 On 28-Oct-26 9:42 AM, Li Zhe wrote: > Memory tiering normally promotes any recently accessed slow-tier page if > the target fast-tier node has enough free space. This preserves the > existing policy of filling available fast memory before relying on > hotness and rate-limit control. > > That is not always the desired policy. Some deployments may intentionally > keep part of a workload's memory on CXL-attached memory, for example to > preserve a desired DRAM/CXL capacity split or bandwidth distribution. With > the free-space bypass, short cold accesses and bursts of hot accesses can > refill the fast tier and pull the workload away from that distribution > whenever DRAM has free space. Currently promotion happens on 1st access. Won't it be more natural to tweak this frequency of access and also the time between successive accesses to prevent promotion due to short cold accesses and bursts of hot accesses rather than free space bypass configuration? Regards, Bharata.