From: "Moger, Babu" <babu.moger@amd.com>
To: "Luck, Tony" <tony.luck@intel.com>, Borislav Petkov <bp@alien8.de>
Cc: "corbet@lwn.net" <corbet@lwn.net>,
"Chatre, Reinette" <reinette.chatre@intel.com>,
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Subject: Re: [PATCH v11 04/13] x86/cpufeatures: Add Bandwidth Monitoring Event Configuration feature flag
Date: Mon, 9 Jan 2023 15:44:30 -0600 [thread overview]
Message-ID: <ecf0abf0-59fe-3898-762c-d9d883925550@amd.com> (raw)
In-Reply-To: <SJ1PR11MB608321F26D729A082BFC6FAEFCFE9@SJ1PR11MB6083.namprd11.prod.outlook.com>
On 1/9/23 15:25, Luck, Tony wrote:
>>> All the QoS(or RDT) features are visible so far. If we make them visible,
>>> users can easily figure out if this specific feature is supported or not.
>> What would be the actual, real-life use case where the presence of those flags
>> in /proc/cpuinfo is really needed?
> It feels like the old "rule" was "make it visible in /proc/cpuid" unless there was some
> good reason NOT to do it. But that has resulted in the "flags" line getting ridiculously
> long and hard for humans to read (141 fields with 926 bytes on my Skylake, more on
> more modern CPUs).
>
> For RDT I don't see a lot of value in knowing that a feature is present ... all of them
> have parameters on how many things they can control/monitor ... so you have to
> either go parse the CPUID leaves, or just mount /sys/fs/resctrl and look in the "info"
> directory to get the extra information you need to do anything with RDT.
>
> I don't know if we'd break anything if we dropped:
>
> cat_l3 cdp_l3 mba cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local
>
> from /proc/cpuinfo.
>
> Perhaps the "rule" should be written in Documentation/{somewhere}?
Actually, these feature bits are referred in Documentation/x86/resctrl.rst
This feature is enabled by the CONFIG_X86_CPU_RESCTRL and the x86
/proc/cpuinfo
flag bits:
===============================================
================================
RDT (Resource Director Technology) Allocation "rdt_a"
CAT (Cache Allocation Technology) "cat_l3", "cat_l2"
CDP (Code and Data Prioritization) "cdp_l3", "cdp_l2"
CQM (Cache QoS Monitoring) "cqm_llc", "cqm_occup_llc"
MBM (Memory Bandwidth Monitoring) "cqm_mbm_total",
"cqm_mbm_local"
MBA (Memory Bandwidth Allocation) "mba"
SMBA (Slow Memory Bandwidth Allocation) "smba"
BMEC (Bandwidth Monitoring Event Configuration) "bmec"
===============================================
================================
So, if we remove them, we need to update here also.
Thanks
Babu
next prev parent reply other threads:[~2023-01-09 21:45 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-09 16:43 [PATCH v11 00/13] x86/resctrl: Support for AMD QoS new features Babu Moger
2023-01-09 16:43 ` [PATCH v11 01/13] x86/resctrl: Replace smp_call_function_many() with on_each_cpu_mask() Babu Moger
2023-01-09 23:26 ` Ashok Raj
2023-01-10 2:23 ` Moger, Babu
2023-01-10 20:58 ` Luck, Tony
2023-01-11 15:42 ` Ashok Raj
2023-01-11 19:05 ` Luck, Tony
2023-01-11 23:21 ` Ashok Raj
2023-01-09 16:43 ` [PATCH v11 02/13] x86/cpufeatures: Add Slow Memory Bandwidth Allocation feature flag Babu Moger
2023-01-09 16:43 ` [PATCH v11 03/13] x86/resctrl: Add a new resource type RDT_RESOURCE_SMBA Babu Moger
2023-01-09 16:43 ` [PATCH v11 04/13] x86/cpufeatures: Add Bandwidth Monitoring Event Configuration feature flag Babu Moger
2023-01-09 18:58 ` Borislav Petkov
2023-01-09 19:49 ` Moger, Babu
2023-01-09 21:07 ` Borislav Petkov
2023-01-09 21:25 ` Luck, Tony
2023-01-09 21:39 ` Borislav Petkov
2023-01-09 21:50 ` Luck, Tony
2023-01-24 11:28 ` Borislav Petkov
2023-01-09 23:43 ` Reinette Chatre
2023-01-24 11:32 ` Borislav Petkov
2023-01-09 21:44 ` Moger, Babu [this message]
2023-01-09 21:51 ` Borislav Petkov
2023-01-09 23:10 ` Moger, Babu
2023-01-24 11:34 ` Borislav Petkov
2023-01-24 14:11 ` Moger, Babu
2023-01-24 15:10 ` Borislav Petkov
2023-01-24 16:06 ` Moger, Babu
2023-01-24 16:59 ` Reinette Chatre
2023-01-24 17:30 ` Moger, Babu
2023-01-24 17:47 ` Reinette Chatre
2023-01-24 19:03 ` Moger, Babu
2023-01-24 19:11 ` Borislav Petkov
2023-01-24 19:23 ` Reinette Chatre
2023-01-24 20:12 ` Moger, Babu
2023-01-09 16:43 ` [PATCH v11 05/13] x86/resctrl: Include new features in command line options Babu Moger
2023-01-09 16:43 ` [PATCH v11 06/13] x86/resctrl: Detect and configure Slow Memory Bandwidth Allocation Babu Moger
2023-01-09 16:43 ` [PATCH v11 07/13] x86/resctrl: Add __init attribute to rdt_get_mon_l3_config() Babu Moger
2023-01-09 16:44 ` [PATCH v11 08/13] x86/resctrl: Support monitor configuration Babu Moger
2023-01-09 16:44 ` [PATCH v11 09/13] x86/resctrl: Add interface to read mbm_total_bytes_config Babu Moger
2023-01-09 16:44 ` [PATCH v11 10/13] x86/resctrl: Add interface to read mbm_local_bytes_config Babu Moger
2023-01-09 16:44 ` [PATCH v11 11/13] x86/resctrl: Add interface to write mbm_total_bytes_config Babu Moger
2023-01-11 22:04 ` Reinette Chatre
2023-01-09 16:44 ` [PATCH v11 12/13] x86/resctrl: Add interface to write mbm_local_bytes_config Babu Moger
2023-01-09 16:44 ` [PATCH v11 13/13] Documentation/x86: Update resctrl.rst for new features Babu Moger
2023-01-11 22:06 ` Reinette Chatre
2023-01-11 22:39 ` Moger, Babu
2023-01-11 22:56 ` Reinette Chatre
2023-01-12 0:39 ` Moger, Babu
2023-01-12 0:47 ` Moger, Babu
2023-01-12 17:30 ` Reinette Chatre
2023-01-12 19:06 ` Moger, Babu
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