linux-kernel - Re: [PATCH 4/4] selftests/resctrl: Adjust SNC support messages

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Date: Thu, 7 Mar 2024 15:41:00 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Tony Luck <tony.luck@...el.com>
CC: "Wieczor-Retman, Maciej" <maciej.wieczor-retman@...el.com>, "Yu, Fenghua"
	<fenghua.yu@...el.com>, Shuah Khan <shuah@...nel.org>, "james.morse@....com"
	<james.morse@....com>, "ilpo.jarvinen@...ux.intel.com"
	<ilpo.jarvinen@...ux.intel.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-kselftest@...r.kernel.org"
	<linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH 4/4] selftests/resctrl: Adjust SNC support messages

Hi Tony,

On 3/7/2024 3:16 PM, Tony Luck wrote:
> On Thu, Mar 07, 2024 at 02:39:08PM -0800, Reinette Chatre wrote:
>> Thank you for the example. I find that significantly easier to
>> understand than a single number in a generic "nodes_per_l3_cache".
>> Especially with potential confusion surrounding inconsistent "nodes"
>> between allocation and monitoring. 
>>
>> How about domain_cpu_list and domain_cpu_map ?
> 
> Reinette,
> 
> Like this (my test system doesn't have SNC, so all domains are the same):
> 
> $ cd /sys/fs/resctrl/info/
> $ grep . */domain*
> L3/domain_cpu_list:0: 0-35,72-107
> L3/domain_cpu_list:1: 36-71,108-143
> L3/domain_cpu_map:0: 0000,00000fff,ffffff00,0000000f,ffffffff
> L3/domain_cpu_map:1: ffff,fffff000,000000ff,fffffff0,00000000
> L3_MON/domain_cpu_list:0: 0-35,72-107
> L3_MON/domain_cpu_list:1: 36-71,108-143
> L3_MON/domain_cpu_map:0: 0000,00000fff,ffffff00,0000000f,ffffffff
> L3_MON/domain_cpu_map:1: ffff,fffff000,000000ff,fffffff0,00000000
> MB/domain_cpu_list:0: 0-35,72-107
> MB/domain_cpu_list:1: 36-71,108-143
> MB/domain_cpu_map:0: 0000,00000fff,ffffff00,0000000f,ffffffff
> MB/domain_cpu_map:1: ffff,fffff000,000000ff,fffffff0,00000000
> 
> 
> The patch to do this is pretty straightforward.
> 

Thank you for looking into this. This looks like valuable information
for user space. Back to what started this discussion ... I expect user
space can compare CPUs associated with control and monitoring domains
to learn if SNC is enabled? (And now existence of domain_cpu_list and/or
domain_cpu_map can also be used to determine if kernel supports SNC).

Reinette