linux-kernel - Re: [PATCH v9 9/9] x86/resctrl: Display RMID of resource group

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Message-ID: <902ae38f-fbd5-2686-0467-ca440e9a7a50@intel.com>
Date:   Tue, 12 Sep 2023 10:57:50 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     <babu.moger@....com>, <corbet@....net>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <bp@...en8.de>
CC:     <fenghua.yu@...el.com>, <dave.hansen@...ux.intel.com>,
        <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
        <akpm@...ux-foundation.org>, <quic_neeraju@...cinc.com>,
        <rdunlap@...radead.org>, <damien.lemoal@...nsource.wdc.com>,
        <songmuchun@...edance.com>, <peterz@...radead.org>,
        <jpoimboe@...nel.org>, <pbonzini@...hat.com>,
        <chang.seok.bae@...el.com>, <pawan.kumar.gupta@...ux.intel.com>,
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        <sandipan.das@....com>, <tony.luck@...el.com>,
        <james.morse@....com>, <linux-doc@...r.kernel.org>,
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        <quic_jiles@...cinc.com>, <peternewman@...gle.com>
Subject: Re: [PATCH v9 9/9] x86/resctrl: Display RMID of resource group

Hi Babu,

On 9/12/2023 10:39 AM, Moger, Babu wrote:
> On 9/11/23 18:08, Reinette Chatre wrote:
>> Hi Babu,
>>
>> On 9/7/2023 4:51 PM, Babu Moger wrote:
>>> In x86, hardware uses RMID to identify a a monitoring group. When a
>>> user creates a monitor group these details are not visible. These details
>>> can help resctrl debugging.
>>>
>>> Add RMID(mon_hw_id) to the monitor groups display in resctrl interface.
>>> Users can see these details when resctrl is mounted with "-o debug" option.
>>>
>>> Other architectures do not use "RMID". Use the name mon_hw_id to refer
>>> to "RMID" in an effort to keep the naming generic.
>>>
>>> Add the flag RFTYPE_MON_BASE, which contains the files required only
>>> for the MON group.
>>
>> As I mentioned in [1] I believe adding support for files with RFTYPE_MON flag
>> to resctrl needs to be in a separate patch. With the core support added a file
>> with this flag can be introduced separately. 
> 
> Yes. We discussed it. Thought it may not fit as a separate patch on its
> own. So, i combined it.
> 
> Now, I split patch 9 into two. Let me know if it looks ok.
> 
> ==========================================================================
> 
> Author: Babu Moger <babu.moger@....com>
> Date:   Thu Sep 7 18:51:28 2023 -0500
> 
>     x86/resctrl: Add RFTYPE_MON_BASE for MON groups
> 
>     Add the flag RFTYPE_MON_BASE, which contains the files required only
>     for the MON group. Files with these flags are only visible when
>     monitoring is enabled.
> 
>     Signed-off-by: Babu Moger <babu.moger@....com>
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h
> b/arch/x86/kernel/cpu/resctrl/internal.h
> index ccdbed615d41..72988e5c52a7 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -296,6 +296,8 @@ struct rdtgroup {
>   *     --> RFTYPE_BASE (Files common for both MON and CTRL groups)
>   *         Files: cpus, cpus_list, tasks
>   *
> + *             --> RFTYPE_MON (Files only for MON group)
> + *
>   *             --> RFTYPE_CTRL (Files only for CTRL group)
>   *                 Files: mode, schemata, size
>   *

I think it would be ok to add above hunk as part of the patch
that adds mon_hw_id, similar to what you did in patch 8.

> @@ -315,6 +317,7 @@ struct rdtgroup {
>  #define RFTYPE_MON_INFO                        (RFTYPE_INFO | RFTYPE_MON)
>  #define RFTYPE_TOP_INFO                        (RFTYPE_INFO | RFTYPE_TOP)
>  #define RFTYPE_CTRL_BASE               (RFTYPE_BASE | RFTYPE_CTRL)
> +#define RFTYPE_MON_BASE                        (RFTYPE_BASE | RFTYPE_MON)
> 

This hunk may be appropriate for patch 3.

>  /* List of all resource groups */
>  extern struct list_head rdt_all_groups;
> 

This is not how I expected it to look. There is currently an issue
in resctrl where files with RFTYPE_MON are not created for CTRL_MON
groups. This has not actually been a problem because there are
no files with the RFTYPE_MON flag. This series introduces the first
file with RFTYPE_MON flag and thus this resctrl issue needs to be fixed
before this new file can be supported.

Considering this I expected to see the changes in rdt_get_tree()
and mkdir_rdt_prepare() done as a separate patch. This will add
support for RFTYPE_MON files to resctrl. After this change
a separate patch can add the file that has this flag.

Reinette