linux-kernel - Re: [PATCH 14/18] x86/resctrl: Add helpers for system wide mon/alloc capable

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Date:   Thu, 24 Nov 2022 14:22:00 +0000
From:   James Morse <james.morse@....com>
To:     "Shaopeng Tan (Fujitsu)" <tan.shaopeng@...itsu.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        "carl@...amperecomputing.com" <carl@...amperecomputing.com>,
        "lcherian@...vell.com" <lcherian@...vell.com>,
        "bobo.shaobowang@...wei.com" <bobo.shaobowang@...wei.com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>,
        "xingxin.hx@...nanolis.org" <xingxin.hx@...nanolis.org>,
        "baolin.wang@...ux.alibaba.com" <baolin.wang@...ux.alibaba.com>,
        "peternewman@...gle.com" <peternewman@...gle.com>
Subject: Re: [PATCH 14/18] x86/resctrl: Add helpers for system wide mon/alloc
 capable

Hello!

On 10/11/2022 10:51, Shaopeng Tan (Fujitsu) wrote:
>> resctrl reads rdt_alloc_capable or rdt_mon_capable to determine whether any
>> of the resources support the corresponding features.
>> resctrl also uses the static-keys that affect the architecture's context-switch
>> code to determine the same thing.
>>
>> This forces another architecture to have the same static-keys.
>>
>> As the static-key is enabled based on the capable flag, and none of the
>> filesystem uses of these are in the scheduler path, move the capable flags
>> behind helpers, and use these in the filesystem code instead of the static-key.
>>
>> After this change, only the architecture code manages and uses the static-keys
>> to ensure __resctrl_sched_in() does not need runtime checks.
>>
>> This avoids multiple architectures having to define the same static-keys.

> arch/x86/kernel/cpu/resctrl/rdtgroup.c
>  static void mkdir_rdt_prepare_rmid_free(struct rdtgroup *rgrp)
>  {
>          if (rdt_mon_capable) 
>                  free_rmid(rgrp->closid, rgrp->mon.rmid);
>  }
> I think you forgot to fix rdt_mon_capable here.
> if (rdt_mon_capable) => if (resctrl_arch_mon_capable())

Yes - looks like I did.


Thanks!

James