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b=jF6tQqlmeyYwVKcpKqU69b8ZPbsH6YY2wYJnoMbdddrwbLxtKa41Mg86MyaobUdIkf/SBjXYlrtm+C4lbctowv6pdEb7b8hVBnNFZTB8j4XVTFvi360L5tMHQnR+84l5oTKvGzoSLg1Zs/i3QpSmys63jFlLYoMzqksXOkgtjo8= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from MW3PR12MB4553.namprd12.prod.outlook.com (2603:10b6:303:2c::19) by DS7PR12MB6333.namprd12.prod.outlook.com (2603:10b6:8:96::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7762.28; Mon, 15 Jul 2024 18:36:38 +0000 Received: from MW3PR12MB4553.namprd12.prod.outlook.com ([fe80::b0ef:2936:fec1:3a87]) by MW3PR12MB4553.namprd12.prod.outlook.com ([fe80::b0ef:2936:fec1:3a87%5]) with mapi id 15.20.7762.027; Mon, 15 Jul 2024 18:36:38 +0000 Message-ID: <4ab74f69-ecd7-4dea-ac92-adcd9923b0bd@amd.com> Date: Mon, 15 Jul 2024 13:36:34 -0500 User-Agent: Mozilla Thunderbird Reply-To: babu.moger@amd.com Subject: Re: [PATCH v5 01/20] x86/cpufeatures: Add support for Assignable Bandwidth Monitoring Counters (ABMC) To: Reinette Chatre , corbet@lwn.net, fenghua.yu@intel.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com Cc: x86@kernel.org, hpa@zytor.com, paulmck@kernel.org, rdunlap@infradead.org, tj@kernel.org, peterz@infradead.org, yanjiewtw@gmail.com, kim.phillips@amd.com, lukas.bulwahn@gmail.com, seanjc@google.com, jmattson@google.com, leitao@debian.org, jpoimboe@kernel.org, rick.p.edgecombe@intel.com, kirill.shutemov@linux.intel.com, jithu.joseph@intel.com, kai.huang@intel.com, kan.liang@linux.intel.com, daniel.sneddon@linux.intel.com, pbonzini@redhat.com, sandipan.das@amd.com, ilpo.jarvinen@linux.intel.com, peternewman@google.com, maciej.wieczor-retman@intel.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, eranian@google.com, james.morse@arm.com References: <724d0234ca56d71f9d8d893806870181d027f556.1720043311.git.babu.moger@amd.com> <1c51aa93-5b86-4361-87d5-3d5d48fac4e6@intel.com> Content-Language: en-US From: "Moger, Babu" In-Reply-To: <1c51aa93-5b86-4361-87d5-3d5d48fac4e6@intel.com> Content-Type: text/plain; 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The >> counters of any other RMIDs which are no longer being tracked will be >> reset to zero. The MBM event counters return "Unavailable" for the RMIDs >> that are not tracked by hardware. So, there can be only limited number of >> groups that can give guaranteed monitoring numbers. With ever changing >> configurations there is no way to definitely know which of these groups >> are being tracked for certain point of time. Users do not have the option >> to monitor a group or set of groups for certain period of time without >> worrying about RMID being reset in between. >> >> The ABMC feature provides an option to the user to assign a hardware >> counter to an RMID and monitor the bandwidth as long as it is assigned. >> The assigned RMID will be tracked by the hardware until the user unassigns >> it manually. There is no need to worry about counters being reset during >> this period. Additionally, the user can specify a bitmask identifying the >> specific bandwidth types from the given source to track with the counter. >> >> Without ABMC enabled, monitoring will work in current mode without >> assignment option. >> >> Linux resctrl subsystem provides the interface to count maximum of two >> memory bandwidth events per group, from a combination of available total >> and local events. Keeping the current interface, users can enable a maximum >> of 2 ABMC counters per group. User will also have the option to enable only >> one counter to the group. If the system runs out of assignable ABMC >> counters, kernel will display an error. Users need to disable an already >> enabled counter to make space for new assignments. >> >> The feature can be detected via CPUID_Fn80000020_EBX_x00 bit 5. >> Bits Description >> 5    ABMC (Assignable Bandwidth Monitoring Counters) >> >> The feature details are documented in APM listed below [1]. >> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming >> Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth >> Monitoring (ABMC). >> >> Note: Checkpatch checks/warnings are ignored to maintain coding style. > > This note may be more appropriate below the '---' separator line. Sure. > >> >> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 >> Signed-off-by: Babu Moger >> --- > > Reviewed-by: Reinette Chatre -- Thanks Babu Moger