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Message-ID: <5b788e1a-d872-e318-1be5-8640fe887b9d@suse.com> Date: Wed, 22 Jun 2022 10:59:50 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [RFC PATCH 1/2] xen/memory : Add stats_table resource type Content-Language: en-US To: Matias Ezequiel Vara Larsen Cc: Matias Ezequiel Vara Larsen , Andrew Cooper , George Dunlap , Julien Grall , Stefano Stabellini , Wei Liu , Dario Faggioli , xen-devel@lists.xenproject.org References: From: Jan Beulich In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AS9PR06CA0362.eurprd06.prod.outlook.com (2603:10a6:20b:460::9) To VE1PR04MB6560.eurprd04.prod.outlook.com (2603:10a6:803:122::25) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: b7b09417-6db9-4261-057e-08da542d8f99 X-MS-TrafficTypeDiagnostic: AS8PR04MB8851:EE_ X-LD-Processed: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba,ExtFwd X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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> + > + // WIP: use a different interface > + runstate = (uint64_t*)v->stats.va; > + memcpy(runstate, &v->runstate.time[0], sizeof(v->runstate.time[0])); > } One remark on top of what George has said: By exposing this information the way you do, you allow updating and reading of it to be fully asynchronous. That way a consumer may fetch inconsistent (partially updated) state (and this would be even more so when further fields would be added). For the data to be useful, you need to add a mechanism for consumers to know when an update is in progress, so they can wait and then retry. You'll find a number of instances of such in the code base. In general I also have to admit that I'm not sure the exposed data really qualifies as a "resource", and hence I'm not really convinced of your use of the resource mapping interface as a vehicle. Jan