Re: [PATCH v4 1/2] x86/resctrl: Pass domain to target CPU

From: Reinette Chatre <reinette.chatre@intel.com>
To: "Luck, Tony" <tony.luck@intel.com>,
	"Yu, Fenghua" <fenghua.yu@intel.com>,
	Peter Newman <peternewman@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Shuah Khan <skhan@linuxfoundation.org>,
	"x86@kernel.org" <x86@kernel.org>
Cc: Shaopeng Tan <tan.shaopeng@fujitsu.com>,
	James Morse <james.morse@arm.com>,
	Jamie Iles <quic_jiles@quicinc.com>,
	Babu Moger <babu.moger@amd.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Drew Fustini <dfustini@baylibre.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"patches@lists.linux.dev" <patches@lists.linux.dev>
Subject: Re: [PATCH v4 1/2] x86/resctrl: Pass domain to target CPU
Date: Mon, 4 Mar 2024 17:31:37 -0800	[thread overview]
Message-ID: <428622f8-8dd9-40c8-8762-6bdef6d3a785@intel.com> (raw)
In-Reply-To: <SJ1PR11MB60839371908CDC17A01F2167FC222@SJ1PR11MB6083.namprd11.prod.outlook.com>

Hi Tony,

On 3/4/2024 4:17 PM, Luck, Tony wrote:
>>> +                   cpu = cpumask_any(&d->cpu_mask);
>>>
>>
>> cpu only needs to be assigned once. How about initializing cpu to
>> nr_cpu_ids at the same time msr_param.res and msr_param.dom is
>> initialized and only assign it when msr_param.res is assigned?
>> I think that will be more robust.
>>
>> If you agree and do this then please feel free to add:
>> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
> 
> Reinette,
> 
> I agree. I'll move the assignment to "cpu" outside the CDP_NUM_TYPES
> loop.
> 

If I understand correctly that would always look for a valid "cpu"
even when none is needed. Not quite what I proposed but should
work. Just some wasted cycles in a non critical path. 

Reinette