Re: [RFC] mpam,x86,fs/resctrl: Generic schema description Proof of Concept

[Babu Moger <babu.moger@amd.com>]

Hi Reinette,

On 6/17/26 12:18, Reinette Chatre wrote:
> Hi Babu,
> 
> On 6/15/26 2:05 PM, Moger, Babu wrote:
>>
>> Re-based GMBA patches[3] on top of this series.
> 
> Thank you very much for trying it out.
> 
>>
>> [3] https://lore.kernel.org/lkml/cover.1776980182.git.babu.moger@amd.com/
>>
>> #sudo mount -t resctrl resctrl /sys/fs/resctrl
>>
>> #cat /sys/fs/resctrl/schemata
>> SMBA_GBL:0=4096;1=4096
>>       SMBA:0=8192;1=8192;2=8192;3=8192
>>     MB_GBL:0=4096;1=4096
>>         MB:0=8192;1=8192;2=8192;3=8192
>>         L3:0=ffff;1=ffff;2=ffff;3=ffff
>>
>>
>> Needed this change to get the schemata alignment correctly.
>>
>> Note: Renamed GMB to MB_GBL and GSMBA to SMBA_GBL.
>>
>> ===========================================================
>> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
>> index 979176b054e8..6123689e1250 100644
>> --- a/fs/resctrl/ctrlmondata.c
>> +++ b/fs/resctrl/ctrlmondata.c
>> @@ -512,17 +512,22 @@ static void show_doms(struct seq_file *s, struct rdt_resource_final *f,
>>   {
>>          struct rdt_resource *r = f->res;
>>          struct rdt_ctrl_domain *dom;
>> +       char res_name[16];
>>          bool sep = false;
>>          u32 ctrl_val;
>>
>>          /* Walking r->domains, ensure it can't race with cpuhp */
>>          lockdep_assert_cpus_held();
>>
>> -       if (print_ctrl)
>> -               seq_printf(s, "%*s%s%s:", max_name_width, f->name,
>> -                               resctrl_ctrl_is_default(ctrl) ? "" : "_",
>> -                               resctrl_ctrl_is_default(ctrl) ?
>> -                                "" : resctrl_ctrl_name_str(ctrl->name));
>> +       if (print_ctrl) {
>> +               if (resctrl_ctrl_is_default(ctrl))
>> +                       snprintf(res_name, sizeof(res_name), "%s", f->name);
>> +               else
>> +                       snprintf(res_name, sizeof(res_name), "%s_%s",
>> +                                       f->name, resctrl_ctrl_name_str(ctrl->name));
>> +               seq_printf(s, "%*s:", max_name_width, res_name);
>> +       }
>> +
>>          list_for_each_entry(dom, &ctrl->domains, hdr.list) {
>>                  if (sep)
>>                          seq_puts(s, ";");
>>
> 
> This looks like a workaround for a bug. Are you perhaps running with Tony's
> fixup included?
> https://lore.kernel.org/lkml/aiB2oJFPF-sqUVQx@agluck-desk3/

Ah.. I missed that.

> 
>> ====================================================================
>>
>> $ tree /sys/fs/resctrl/info/MB/
>> /sys/fs/resctrl/info/MB/
>> ├── bandwidth_gran
>> ├── delay_linear
>> ├── min_bandwidth
>> ├── num_closids
>> └── resource_schemata
>>      ├── MB
>>      │   ├── max
>>      │   ├── min
>>      │   ├── resolution
>>      │   ├── scale
>>      │   ├── scope
>>      │   ├── tolerance
>>      │   ├── type
>>      │   └── unit
>>      └── MB_GBL
>>          ├── max
>>          ├── min
>>          ├── resolution
>>          ├── scale
>>          ├── scope
>>          ├── tolerance
>>          ├── type
>>          └── unit
>>
>> 4 directories, 20 files
>>
>>
>> $ tree /sys/fs/resctrl/info/SMBA/
>> /sys/fs/resctrl/info/SMBA/
>> ├── bandwidth_gran
>> ├── delay_linear
>> ├── min_bandwidth
>> ├── num_closids
>> └── resource_schemata
>>      ├── SMBA
>>      │   ├── max
>>      │   ├── min
>>      │   ├── resolution
>>      │   ├── scale
>>      │   ├── scope
>>      │   ├── tolerance
>>      │   ├── type
>>      │   └── unit
>>      └── SMBA_GBL
>>          ├── max
>>          ├── min
>>          ├── resolution
>>          ├── scale
>>          ├── scope
>>          ├── tolerance
>>          ├── type
>>          └── unit
>>
>> 4 directories, 20 files
>>
>> Does the info directory hierarchy look right?
> 
> I am not sure if the "GBL" extension is most informative. In this thread there
> were some motivations for the control names to include the scope. It could be useful
> to create some control naming customs to not have the schemata file become chaotic.

Make sense.

> Apart from that the hierarchy above matches what we have so far for the new schema
> descriptions.
> 
> Could you please also share the contents of the new files resulting from this
> implementation?

Used this script to print:

$tree -fi info/MB | while read f; do
     if [ -f "$f" ]; then
         printf "%s: %s\n" "$f" "$(cat "$f")"
     else
         echo "$f"
     fi
done


info/MB
info/MB/bandwidth_gran: 1
info/MB/delay_linear: 0
info/MB/min_bandwidth: 0
info/MB/num_closids: 16
info/MB/resource_schemata
info/MB/resource_schemata/MB
info/MB/resource_schemata/MB/max: 8192
info/MB/resource_schemata/MB/min: 0
info/MB/resource_schemata/MB/resolution: 8
info/MB/resource_schemata/MB/scale: 1
info/MB/resource_schemata/MB/scope: L3
info/MB/resource_schemata/MB/tolerance: 0
info/MB/resource_schemata/MB/type: scalar
info/MB/resource_schemata/MB/unit: GBps
info/MB/resource_schemata/MB_GBL
info/MB/resource_schemata/MB_GBL/max: 4096
info/MB/resource_schemata/MB_GBL/min: 0
info/MB/resource_schemata/MB_GBL/resolution: 1
info/MB/resource_schemata/MB_GBL/scale: 1
info/MB/resource_schemata/MB_GBL/scope: Unsupported control scope
info/MB/resource_schemata/MB_GBL/tolerance: 0
info/MB/resource_schemata/MB_GBL/type: scalar
info/MB/resource_schemata/MB_GBL/unit: GBps

4 directories, 20 files


info/SMBA
info/SMBA/bandwidth_gran: 1
info/SMBA/delay_linear: 0
info/SMBA/min_bandwidth: 0
info/SMBA/num_closids: 16
info/SMBA/resource_schemata
info/SMBA/resource_schemata/SMBA
info/SMBA/resource_schemata/SMBA/max: 8192
info/SMBA/resource_schemata/SMBA/min: 0
info/SMBA/resource_schemata/SMBA/resolution: 8
info/SMBA/resource_schemata/SMBA/scale: 1
info/SMBA/resource_schemata/SMBA/scope: L3
info/SMBA/resource_schemata/SMBA/tolerance: 0
info/SMBA/resource_schemata/SMBA/type: scalar
info/SMBA/resource_schemata/SMBA/unit: GBps
info/SMBA/resource_schemata/SMBA_GBL
info/SMBA/resource_schemata/SMBA_GBL/max: 4096
info/SMBA/resource_schemata/SMBA_GBL/min: 0
info/SMBA/resource_schemata/SMBA_GBL/resolution: 1
info/SMBA/resource_schemata/SMBA_GBL/scale: 1
info/SMBA/resource_schemata/SMBA_GBL/scope: Unsupported control scope
info/SMBA/resource_schemata/SMBA_GBL/tolerance: 0
info/SMBA/resource_schemata/SMBA_GBL/type: scalar
info/SMBA/resource_schemata/SMBA_GBL/unit: GBps

4 directories, 20 files


> 
>> After going through the comments, it seems like it should cover most
>> of the upcoming features. At least the Global MBA/SMBA stuff looks
>> like it fits in well with the RFC.
> 
> That is good news.
> 
>> What is your expectation for the RFC going forward?
> 
> The "opens" of the RFC needs to be finalized as well as the items identified during this
> discussion. How to support emulated controls looks to be the biggest one. While the
> initial schema description may not need to support emulated controls, how to support
> it needs to be clear since the initial schema description needs to be accompanied
> with enough user documentation to support such future change.
> 
> It should be possible to start upstreaming at least the preparatory patches.
> 

Sounds good. Will keep an eye out for it.
Thanks
Babu