linux-kernel - Re: [PATCH 3/7] x86/resctrl: Add a new node-scoped resource to rdt_resources

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Date:   Sat, 28 Jan 2023 02:25:42 +0000
From:   "Yu, Fenghua" <fenghua.yu@...el.com>
To:     "Luck, Tony" <tony.luck@...el.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        Peter Newman <peternewman@...gle.com>,
        "Jonathan Corbet" <corbet@....net>,
        "x86@...nel.org" <x86@...nel.org>
CC:     Shaopeng Tan <tan.shaopeng@...itsu.com>,
        James Morse <james.morse@....com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Babu Moger <babu.moger@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: Re: [PATCH 3/7] x86/resctrl: Add a new node-scoped resource to
 rdt_resources_all[]

Hi, Tony,

On 1/27/23 10:23, Luck, Tony wrote:
>>> +	[RDT_RESOURCE_NODE] =
>>> +	{
>>> +		.r_resctrl = {
>>> +			.rid			= RDT_RESOURCE_NODE,
>>> +			.name			= "L3",
> 
>> "L3" was named as RDT_RESOURCE_L3 already. The duplicate name here may
>> cause duplicate file names in info dir. Maybe rename it as "L3_NODE"?
> 
> I thought the same, and my first implementation used a different string here (I picked
> "NODE" rather than "L3_NODE").
> 
> But my testers complained that this broke all their existing infrastructure that reads
> cache occupancy and memory bandwidth. This string is not just used in the info/
> directory, it is also the basis for the directory names in mon_data/
> 
> $ tree /sys/fs/resctrl/mon_data
> /sys/fs/resctrl/mon_data
> ├── mon_L3_00
> │   ├── llc_occupancy
> │   ├── mbm_local_bytes
> │   └── mbm_total_bytes
> ├── mon_L3_01
> │   ├── llc_occupancy
> │   ├── mbm_local_bytes
> │   └── mbm_total_bytes
> ├── mon_L3_02
> │   ├── llc_occupancy
> │   ├── mbm_local_bytes
> │   └── mbm_total_bytes
> └── mon_L3_03
>      ├── llc_occupancy
>      ├── mbm_local_bytes
>      └── mbm_total_bytes
> 
> The name using "L3" is still appropriate and accurate.
> 
> There isn't a "duplicate file names" problem in the info/ directory because a system
> either has SNC disabled, and uses the L3-scoped resource, or has SNC enabled and
> uses the node-scoped resource.

That's right.

Thank you for your info!

-Fenghua