linux-kernel - Re: [RFC PATCH v3 00/17] x86/resctrl : Support AMD Assignable Bandwidth Monitoring Counters (ABMC)

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Date: Tue, 23 Apr 2024 10:43:25 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Dave Martin <Dave.Martin@....com>, Peter Newman <peternewman@...gle.com>
Cc: corbet@....net, fenghua.yu@...el.com, reinette.chatre@...el.com,
 tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
 paulmck@...nel.org, rdunlap@...radead.org, tj@...nel.org,
 peterz@...radead.org, yanjiewtw@...il.com, kim.phillips@....com,
 lukas.bulwahn@...il.com, seanjc@...gle.com, jmattson@...gle.com,
 leitao@...ian.org, jpoimboe@...nel.org, rick.p.edgecombe@...el.com,
 kirill.shutemov@...ux.intel.com, jithu.joseph@...el.com,
 kai.huang@...el.com, kan.liang@...ux.intel.com,
 daniel.sneddon@...ux.intel.com, pbonzini@...hat.com, sandipan.das@....com,
 ilpo.jarvinen@...ux.intel.com, maciej.wieczor-retman@...el.com,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, eranian@...gle.com,
 james.morse@....com
Subject: Re: [RFC PATCH v3 00/17] x86/resctrl : Support AMD Assignable
 Bandwidth Monitoring Counters (ABMC)

Hi Dave,

On 4/23/24 07:38, Dave Martin wrote:
> Hi Peter,
> 
> On Mon, Apr 22, 2024 at 11:23:50AM -0700, Peter Newman wrote:
>> Hi Dave,
>>
>> On Mon, Apr 22, 2024 at 9:33 AM Dave Martin <Dave.Martin@....com> wrote:
>>>
>>> Hi Babu,
>>>
>>> On Thu, Mar 28, 2024 at 08:06:33PM -0500, Babu Moger wrote:
>>>>        Assignment flags can be one of the following:
>>>>
>>>>         t  MBM total event is assigned
>>>
>>> With my MPAM hat on this looks a bit weird, although I suppose it
>>> follows on from the way "mbm_total_bytes" and "mbm_local_bytes" are
>>> already exposed in resctrlfs.
>>>
>>> From an abstract point of view, "total" and "local" are just event
>>> selection criteria, additional to those in mbm_cfg_mask.  The different
>>> way they are treated in the hardware feels like an x86 implementation
>>> detail.
>>>
>>> For MPAM we don't currently distinguish local from non-local traffic, so
>>> I guess this just reduces to a simple on-off (i.e., "t" or nothing),
>>> which I guess is tolerable.
>>>
>>> This might want more thought if there is an expectation that more
>>> categories will be added here, though (?)
>>
>> There should be a path forward whenever we start supporting
>> user-configured counter classes. I assume the letters a-z will be
>> enough to cover all the counter classes which could be used at once.
> 
> Ack, though I'd appreciate a response on the point about "_" below in
> case people missed it.

It was based on the dynamic debug interface and also Reinette's suggestion
as well.
https://www.kernel.org/doc/html/v4.10/admin-guide/dynamic-debug-howto.html
(Look for "No flags are set").

We tried to use that similar interface.
-- 
Thanks
Babu Moger