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Message-ID: <f791d0e5-43b2-8ec2-436b-c008d2ce7696@intel.com>
Date: Mon, 28 Aug 2023 10:06:32 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Tony Luck <tony.luck@...el.com>
CC: Fenghua Yu <fenghua.yu@...el.com>,
Peter Newman <peternewman@...gle.com>,
Jonathan Corbet <corbet@....net>,
Shuah Khan <skhan@...uxfoundation.org>, <x86@...nel.org>,
Shaopeng Tan <tan.shaopeng@...itsu.com>,
James Morse <james.morse@....com>,
Jamie Iles <quic_jiles@...cinc.com>,
Babu Moger <babu.moger@....com>,
Randy Dunlap <rdunlap@...radead.org>,
<linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<patches@...ts.linux.dev>
Subject: Re: [PATCH v4 7/7] selftests/resctrl: Adjust effective L3 cache size
when SNC enabled
Hi Tony,
On 8/25/2023 10:56 AM, Tony Luck wrote:
> On Fri, Aug 11, 2023 at 10:33:43AM -0700, Reinette Chatre wrote:
>> Hi Tony,
>>
>> On 7/22/2023 12:07 PM, Tony Luck wrote:
...
>>> @@ -190,6 +245,8 @@ int get_cache_size(int cpu_no, char *cache_type, unsigned long *cache_size)
>>> break;
>>> }
>>>
>>> + if (cache_num == 3)
>>> + *cache_size /= snc_ways();
>>> return 0;
>>> }
>>>
>>
>> I am surprised that this small change is sufficient. The resctrl
>> selftests are definitely not NUMA aware and the CAT and CMT tests
>> are not taking that into account when picking CPUs to run on. From
>> what I understand LLC occupancy counters need to be added in this
>> scenario but I do not see that done either.
>
> This is a first step (the tests are definitely going to fail if
> they have incorrect information about the cache size).
>
> For a fully reliable set of tests some major surgery will be required
> to bind to CPUs and memory to control allocation and access.
>
What is the plan for making the tests more reliable? What is the
use of this patch if it is just the first step?
Reinette
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