linux-kernel - Re: [PATCH v3 07/26] x86/resctrl: Move L3 initialization out of domain_add_cpu

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Message-ID: <8d5add17-fbe7-4d80-a2cc-31749a052d5b@intel.com>
Date: Tue, 22 Apr 2025 11:18:48 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: "Luck, Tony" <tony.luck@...el.com>
CC: Fenghua Yu <fenghuay@...dia.com>, Maciej Wieczor-Retman
	<maciej.wieczor-retman@...el.com>, Peter Newman <peternewman@...gle.com>,
	James Morse <james.morse@....com>, Babu Moger <babu.moger@....com>, "Drew
 Fustini" <dfustini@...libre.com>, Dave Martin <Dave.Martin@....com>, "Anil
 Keshavamurthy" <anil.s.keshavamurthy@...el.com>,
	<linux-kernel@...r.kernel.org>, <patches@...ts.linux.dev>
Subject: Re: [PATCH v3 07/26] x86/resctrl: Move L3 initialization out of
 domain_add_cpu_mon()

Hi Tony,

On 4/21/25 1:01 PM, Luck, Tony wrote:
> On Fri, Apr 18, 2025 at 02:51:01PM -0700, Reinette Chatre wrote:
>> Hi Tony,
>>
>> On 4/7/25 4:40 PM, Tony Luck wrote:
>>> To prepare for additional types of monitoring domains, move all the
>>> L3 specific initialization into a helper function.
>>>
>>> Signed-off-by: Tony Luck <tony.luck@...el.com>
>>> ---
>>>  arch/x86/kernel/cpu/resctrl/core.c | 57 ++++++++++++++++++------------
>>>  1 file changed, 35 insertions(+), 22 deletions(-)
>>>
>>> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
>>> index d82a4a2db699..703423b0be0e 100644
>>> --- a/arch/x86/kernel/cpu/resctrl/core.c
>>> +++ b/arch/x86/kernel/cpu/resctrl/core.c
>>> @@ -493,33 +493,12 @@ static void domain_add_cpu_ctrl(int cpu, struct rdt_resource *r)
>>>  	}
>>>  }
>>>  
>>> -static void domain_add_cpu_mon(int cpu, struct rdt_resource *r)
>>> +static void setup_l3_mon_domain(int cpu, int id, struct rdt_resource *r, struct list_head *add_pos)
>>>  {
>>> -	int id = get_domain_id_from_scope(cpu, r->mon_scope);
>>> -	struct list_head *add_pos = NULL;
>>>  	struct rdt_hw_mon_domain *hw_dom;
>>> -	struct rdt_domain_hdr *hdr;
>>>  	struct rdt_mon_domain *d;
>>>  	int err;
>>>  
>>> -	lockdep_assert_held(&domain_list_lock);
>>> -
>>> -	if (id < 0) {
>>> -		pr_warn_once("Can't find monitor domain id for CPU:%d scope:%d for resource %s\n",
>>> -			     cpu, r->mon_scope, r->name);
>>> -		return;
>>> -	}
>>> -
>>> -	hdr = resctrl_find_domain(&r->mon_domains, id, &add_pos);
>>> -	if (hdr) {
>>> -		if (WARN_ON_ONCE(hdr->type != DOMTYPE(r->rid, DOMTYPE_MON)))
>>> -			return;
>>> -		d = container_of(hdr, struct rdt_mon_domain, hdr);
>>> -
>>> -		cpumask_set_cpu(cpu, &d->hdr.cpu_mask);
>>> -		return;
>>> -	}
>>> -
>>
>> Many functions called by this new "setup_l3_mon_domain()" are specific to L3 resource but
>> since L3 resource has so far been the only one supported the naming has been generic. Now that
>> this function is made resource specific I think it will help make the code clear if the
>> L3 specific functions called by it are also renamed. For example, mon_domain_free() can
>> be renamed to free_l3_mon_domain() to match the "setup_l3_mon_domain()" introduced here. Also
>> arch_mon_domain_online() -> arch_l3_mon_domain_online().
> 
> What about "struct rdt_mon_domain"? It is now specific to L3. Should I
> change that to rdt_l3_mon_domain" as well (60 lines affected)?
> 
> Ditto for rdt_hw_mon_domain (but only 12 lines for this one).

Thank you for considering this. My vote would be "yes" for both. I think it will help
understand and maintain the code if naming helps to make obvious what data/code applies to.
Monitoring has been synonymous with L3 monitoring for so long that there may be many
instances of this implicit assumption. 

Reinette