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Date: Tue, 23 Apr 2024 17:17:27 +0100
From: Dave Martin <Dave.Martin@arm.com>
To: "Moger, Babu" <babu.moger@amd.com>
Cc: Peter Newman <peternewman@google.com>, corbet@lwn.net,
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Subject: Re: [RFC PATCH v3 00/17] x86/resctrl : Support AMD Assignable
 Bandwidth Monitoring Counters (ABMC)
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In-Reply-To: <4cd220cc-2e8e-4193-b01a-d3cd798c7118@amd.com>

Hi Babu,

On Tue, Apr 23, 2024 at 10:43:25AM -0500, Moger, Babu wrote:
> 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@arm.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.

Fair enough; I haven't touched dynamic debug for quite a while and had
forgotten about this convention being used there.

Apologies for the noise on that!

Cheers
---Dave