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

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Message-ID: <10e7de42-d0c4-45d8-a9f8-bd8e9d4b84db@intel.com>
Date: Tue, 5 Mar 2024 08:48:51 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: "Luck, Tony" <tony.luck@...el.com>, "Yu, Fenghua" <fenghua.yu@...el.com>,
	Peter Newman <peternewman@...gle.com>, Jonathan Corbet <corbet@....net>,
	Shuah Khan <skhan@...uxfoundation.org>, "x86@...nel.org" <x86@...nel.org>
CC: 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>, Drew Fustini
	<dfustini@...libre.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-doc@...r.kernel.org"
	<linux-doc@...r.kernel.org>, "patches@...ts.linux.dev"
	<patches@...ts.linux.dev>
Subject: Re: [PATCH v4 1/2] x86/resctrl: Pass domain to target CPU

Hi Tony,

On 3/5/2024 8:37 AM, Luck, Tony wrote:
>> 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,
> 
> Sorry for misunderstanding. You are right. Assignment to msr_param.dom
> can also be deferred to the same point. Like this:
> 
>         list_for_each_entry(d, &r->domains, list) {
>                 hw_dom = resctrl_to_arch_dom(d);
>                 msr_param.res = NULL;
>                 for (t = 0; t < CDP_NUM_TYPES; t++) {
>                         cfg = &hw_dom->d_resctrl.staged_config[t];
>                         if (!cfg->have_new_ctrl)
>                                 continue;
> 
>                         idx = get_config_index(closid, t);
>                         if (cfg->new_ctrl == hw_dom->ctrl_val[idx])
>                                 continue;
>                         hw_dom->ctrl_val[idx] = cfg->new_ctrl;
> 
>                         if (!msr_param.res) {
>                                 msr_param.low = idx;
>                                 msr_param.high = msr_param.low + 1;
>                                 msr_param.res = r;
>                                 msr_param.dom = d;
>                                 cpu = cpumask_any(&d->cpu_mask);
>                         } else {
>                                 msr_param.low = min(msr_param.low, idx);
>                                 msr_param.high = max(msr_param.high, idx + 1);
>                         }
>                 }
>                 if (msr_param.res)
>                         smp_call_function_single(cpu, rdt_ctrl_update, &msr_param, 1);
>         }

This looks good to me. 

Thank you very much.

Reinette