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b=LHKqgYg3FFeVwq6Vyc3+8mhpSyJBBGBW49iXOvpTdi/ROLcb/ptYWxDsRiPykAluczOK0FAvXwEwOcLZeQCG1i8RSJkcBUyVFk1Iun3Oo0McEDuVshrxXtS4fQIyIJkLXNWs/chJQh6WYMqSRy5gOTky8FrBMpN1PkAvVhLuJzs= Authentication-Results: mx.microsoft.com 1; dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from BL1PR12MB5320.namprd12.prod.outlook.com (2603:10b6:208:314::17) by SA1PR12MB9471.namprd12.prod.outlook.com (2603:10b6:806:458::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.496.15; Wed, 7 Oct 2026 23:47:55 +0000 Received: from BL1PR12MB5320.namprd12.prod.outlook.com ([fe80::1876:4a6d:2cf5:b8d1]) by BL1PR12MB5320.namprd12.prod.outlook.com ([fe80::1876:4a6d:2cf5:b8d1%5]) with mapi id 15.21.0496.015; Wed, 7 Oct 2026 23:47:54 +0000 Message-ID: <8bd1c37e-df79-4c3d-8fad-cfa9443239b2@amd.com> Date: Wed, 7 Oct 2026 18:47:51 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/3] x86,fs/resctrl: Keep mbm_assign_mode in default mode at boot To: Reinette Chatre , Babu Moger , tony.luck@intel.com, bp@alien8.de Cc: x86@kernel.org, Dave.Martin@arm.com, james.morse@arm.com, corbet@lwn.net, skhan@linuxfoundation.org, rdunlap@infradead.org, tglx@kernel.org, mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com, kas@kernel.org, rick.p.edgecombe@intel.com, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org References: <200d21ee-3041-40f2-9032-18e8544a7030@intel.com> Content-Language: en-US From: "Moger, Babu" In-Reply-To: Content-Type: text/plain; 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That breaks the pqos tool [1], which assumes the historical >>>> default mode. pqos treats a non-numeric event read as zero bandwidth. It >>>> creates 16 or more monitoring groups and uses two counters per group. >>>> On a platform with 32 counters per domain, that consumes the pool, so >>>> further groups read "Unassigned" and pqos reports 0 MB/s for them: >>>> >>>>    $sudo pqos -m all:0-4 >>>>    CORE         IPC      MISSES     LLC[KB]   MBL[MB/s]   MBR[MB/s] >>>>       0        0.69         16k       192.0         0.0         0.0 >>>>       1        0.40          3k         0.0         0.0         0.0 >>>>       2        0.44          1k        64.0         0.0         0.0 >>>>       3        0.39          1k        64.0         0.0         0.0 >>>>       4        0.43          1k         0.0         0.0         0.0 >>>> >>>> Leave mbm_assign_mode in "default" mode during initialization. Default >>>> mode uses one counter per monitoring group. On existing AMD platforms >>>> that pool is 64 counters and may be larger on newer hardware. The >>>> "mbm_event" mode uses two counters per group, so 32 counters cover only >>>> 16 groups. >>>> >>>> Deployments within that pool receive accurate bandwidth measurements >>>> with default mode. The hardware supports 4096 monitoring groups. Beyond >>>> that pool, readings may be misleading or "Unavailable", with no >>> >>> At this point I am lost because the word "pool" is used to mean three >>> different things. It is used for the number of "ABMC counters" as well >>> as the number of "non-ABMC counters" that exist on the same platform, >>> above it seems to be used for number of RMIDs (number of monitoring >>> groups) also. Could you please add some context at beginning of >>> changelog to introduce the various counts applicable to the description, >>> associate unique terms to these counts at that time, and then use >>> those unique terms in the rest of the changelog? >> >> Sure. >> I can name as "ABMC counters pool" and "default active counters pool" > > hmmm ... "active counter" is new term that, when grepping this series, > fs/resctrl/*, and arch/x86/kernel/cpu/resctrl/*, does not appear a single > time. > If this new term is needed then please include a definition as part of the > changelog context that makes it obvious what it refers to. > Sure. Will do. Thanks Babu