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Fri, 21 Mar 2025 00:19:44 +0000 Message-ID: <93bca2e4-c91c-40f4-984f-61b3a03af8c2@intel.com> Date: Fri, 21 Mar 2025 08:25:12 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 08/18] iommufd/device: Replace device_list with device_array To: Jason Gunthorpe CC: , , , , References: <20250320134744.5777-1-yi.l.liu@intel.com> <20250320134744.5777-9-yi.l.liu@intel.com> <20250320172057.GA206770@nvidia.com> Content-Language: en-US From: Yi Liu In-Reply-To: <20250320172057.GA206770@nvidia.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SI1PR02CA0003.apcprd02.prod.outlook.com (2603:1096:4:1f7::20) To DS0PR11MB7529.namprd11.prod.outlook.com (2603:10b6:8:141::20) Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR11MB7529:EE_|PH8PR11MB6754:EE_ X-MS-Office365-Filtering-Correlation-Id: cb51a9bd-debf-479f-4a12-08dd680e14a7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016|7053199007; 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>> >> +static int iommufd_group_device_num(struct iommufd_group *igroup) >> +{ >> + struct iommufd_device *idev; >> + unsigned long index; >> + int count = 0; > > unsigned int and unsigned int return code too got it. >> + rc = xa_insert(&igroup->attach->device_array, idev->obj.id, XA_ZERO_ENTRY, >> + GFP_KERNEL); > > Probably don't really care, but note the choice of obj.id here is > going to waste some memory in the xarray. 0 based would be more > memory efficient, but some of the other operations would be slower. yes. The iommufd_device_is_attached() and the detach path might be slower since it would need to loop all the devices. I also considered to store the id for indexing the device_array. But the problem is idev can be stored in multiple device_arrays. A single id does not just like a single list_head cannot work. Seems no better choice... > Reviewed-by: Jason Gunthorpe > > Jason -- Regards, Yi Liu