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

From: Reinette Chatre <reinette.chatre@intel.com>
To: Tony Luck <tony.luck@intel.com>
Cc: "Wieczor-Retman, Maciej" <maciej.wieczor-retman@intel.com>,
	"Yu, Fenghua" <fenghua.yu@intel.com>,
	Shuah Khan <shuah@kernel.org>,
	"james.morse@arm.com" <james.morse@arm.com>,
	"ilpo.jarvinen@linux.intel.com" <ilpo.jarvinen@linux.intel.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-kselftest@vger.kernel.org"
	<linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH 4/4] selftests/resctrl: Adjust SNC support messages
Date: Thu, 7 Mar 2024 15:41:00 -0800	[thread overview]
Message-ID: <83b12a33-6841-40dd-a825-b4db7dbf22db@intel.com> (raw)
In-Reply-To: <ZepK4mtoV_J8-UbE@agluck-desk3>

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