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b=M4BgPzEd4Alwmtz+uj2bUgg+Atf0r7Q0XiimQ8EZME7WlgpD6Ho52At+GMAuHq8iKVb9wizx9RNj9XBVsuAnbGSbW5Do74vsEmPUbFRpfcBF1Y/hFl94xgIgcaZBKCAcp6ONnaHyCw7MFjiH7msP+JF90WyD1s1DRg6PJe84yz4= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from IA0PPF9A76BB3A6.namprd12.prod.outlook.com (2603:10b6:20f:fc04::bdc) by DM4PR12MB7743.namprd12.prod.outlook.com (2603:10b6:8:101::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9137.14; Fri, 19 Sep 2025 19:38:29 +0000 Received: from IA0PPF9A76BB3A6.namprd12.prod.outlook.com ([fe80::8d61:56ca:a8ea:b2eb]) by IA0PPF9A76BB3A6.namprd12.prod.outlook.com ([fe80::8d61:56ca:a8ea:b2eb%8]) with mapi id 15.20.9115.018; Fri, 19 Sep 2025 19:38:28 +0000 Message-ID: <4da93c53-54ae-4599-ba40-3ba1cddd5b8e@amd.com> Date: Fri, 19 Sep 2025 14:38:22 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 07/10] fs/resctrl: Introduce interface to display io_alloc CBMs To: Reinette Chatre , Babu Moger , corbet@lwn.net, tony.luck@intel.com, Dave.Martin@arm.com, james.morse@arm.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com Cc: x86@kernel.org, hpa@zytor.com, kas@kernel.org, rick.p.edgecombe@intel.com, akpm@linux-foundation.org, paulmck@kernel.org, pmladek@suse.com, pawan.kumar.gupta@linux.intel.com, rostedt@goodmis.org, kees@kernel.org, arnd@arndb.de, fvdl@google.com, seanjc@google.com, thomas.lendacky@amd.com, manali.shukla@amd.com, perry.yuan@amd.com, sohil.mehta@intel.com, xin@zytor.com, peterz@infradead.org, mario.limonciello@amd.com, gautham.shenoy@amd.com, nikunj@amd.com, dapeng1.mi@linux.intel.com, ak@linux.intel.com, chang.seok.bae@intel.com, ebiggers@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org References: <382926e0decbe8d64df56c857fdf10feef6fcc51.1756851697.git.babu.moger@amd.com> <2c3a8282-e876-4cdb-8355-0fd78eb6c0b4@intel.com> Content-Language: en-US From: "Moger, Babu" In-Reply-To: <2c3a8282-e876-4cdb-8355-0fd78eb6c0b4@intel.com> Content-Type: text/plain; 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Since the resource name is part of the path, it >> is not necessary to display the resource name as done in the schemata file. >> Pass the resource name to show_doms() and print it only if the name is >> valid. For io_alloc, pass NULL pointer to suppress printing the resource >> name. > > Related to changelog feedback received during ABMC series I think the portion > that describes the code (from "Pass the resource name ..." to "printing the > resource name"), is unnecessary since it can be seen by looking at the patch. Sure. > >> >> When CDP is enabled, io_alloc routes traffic using the highest CLOSID >> associated with the L3CODE resource. To ensure consistent cache allocation >> behavior, the L3CODE and L3DATA resources are kept in sync. So, the > > I do not think the "To ensure consistent cache allocation behavior" is accurate. > This is just to avoid the possible user space confusion if supporting the feature > with L3CODE used for I/O allocation and L3DATA becomes unusable, no? Yes. that is correct. > > Also, this also needs to be in imperative tone. > >> Capacity Bit Masks (CBMs) accessed through either L3CODE or L3DATA will >> reflect identical values. > > Attempt to put it together, please feel free to improve: > > Introduce the "io_alloc_cbm" resctrl file to display the Capacity Bit > Masks (CBMs) that represent the portions of each cache instance allocated > for I/O traffic on a cache resource that supports the "io_alloc" feature. > > io_alloc_cbm resides in the info directory of a cache resource, for example, > /sys/fs/resctrl/info/L3/. Since the resource name is part of the path, it > is not necessary to display the resource name as done in the schemata file. > > When CDP is enabled, io_alloc routes traffic using the highest CLOSID > associated with the L3CODE resource and that CLOSID becomes unusable for > the L3DATA resource. The highest CLOSID of L3CODE and L3DATA resources will > be kept in sync to ensure consistent user interface. In preparation for this, > access the CBMs for I/O traffic through highest CLOSID of either L3CODE or > L3DATA resource. > Looks good. >> >> Signed-off-by: Babu Moger >> --- > > .. > >> @@ -807,3 +809,40 @@ ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf, >> >> return ret ?: nbytes; >> } >> + >> +int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, struct seq_file *seq, void *v) >> +{ >> + struct resctrl_schema *s = rdt_kn_parent_priv(of->kn); >> + struct rdt_resource *r = s->res; >> + int ret = 0; >> + >> + cpus_read_lock(); >> + mutex_lock(&rdtgroup_mutex); >> + >> + rdt_last_cmd_clear(); >> + >> + if (!r->cache.io_alloc_capable) { >> + rdt_last_cmd_printf("io_alloc is not supported on %s\n", s->name); >> + ret = -ENODEV; >> + goto out_unlock; >> + } >> + >> + if (!resctrl_arch_get_io_alloc_enabled(r)) { >> + rdt_last_cmd_printf("io_alloc is not enabled on %s\n", s->name); >> + ret = -EINVAL; > > The return code when io_alloc is not enabled is different between reading from (EINVAL) and > writing to (ENODEV) io_alloc_cbm. Please be consistent. Will change the return code in patch 9 to -EINVAL to be consistent. > >> + goto out_unlock; >> + } >> + >> + /* >> + * When CDP is enabled, resctrl_io_alloc_init_cbm() sets the same CBM for >> + * both L3CODE and L3DATA of the highest CLOSID. As a result, the io_alloc > > Not just during initialization, they are kept in sync during runtime also (when > user writes to io_alloc_cbm). First sentence can perhaps just be > "When CDP is enabled the CBMs of the highest CLOSID of L3CODE > and L3DATA are kept in sync. As a result, ..." > Sure. Thanks Babu