linux-kernel - Re: [PATCH 05/24] x86/resctrl: Pass the schema in resdir's private pointer

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Message-ID: <892c8c20-92e3-750f-00cf-8d559b0d181b@arm.com>
Date:   Fri, 12 Mar 2021 17:11:06 +0000
From:   James Morse <james.morse@....com>
To:     Reinette Chatre <reinette.chatre@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        shameerali.kolothum.thodi@...wei.com,
        Jamie Iles <jamie@...iainc.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>
Subject: Re: [PATCH 05/24] x86/resctrl: Pass the schema in resdir's private
 pointer

Hi Reinette,

On 17/11/2020 21:49, Reinette Chatre wrote:
> It is not clear what "resdir" mentioned in subject line refers to.

rdtgroup_mkdir_info_resdir(), it looks I picked the wrong bit to identify it.
('info' in a name usually conveys no information at all!)


> Could it be changed to "info dir"?

Sure,


> On 10/30/2020 9:11 AM, James Morse wrote:
>> Moving properties that resctrl exposes to user-space into the core
>> 'fs' code, (e.g. the name of the schema), means some of the functions
>> that back the filesystem need the schema struct, but currently take the
>> resource.
> 
> I think a simple addition would help to parse the above ...
> 
> " ... need the schema struct (to where the properties are moved), ..."
> 
>>
>> Once the CDP resources are merged, the resource doesn't reflect the
>> right level of information.
>>
>> For the info dirs that represent a control, the information needed
>> is in the schema, as this is how the resource is being used. For the
>> monitors, its the resource as L3CODE_MON doesn't make sense, and would
>> monitor data too.
>>
>> This difference means the type of the private pointers varies
>> between control and monitor info dirs.
>>
>> If the flags are RF_MON_INFO, its a struct rdt_resource. If the
>> flags are RF_CTRL_INFO, its a struct resctrl_schema. Nothing in
>> res_common_files[] has both flags.

>> @@ -1794,6 +1803,7 @@ static int rdtgroup_mkdir_info_resdir(struct rdt_resource *r, char
>> *name,
>>     static int rdtgroup_create_info_dir(struct kernfs_node *parent_kn)
>>   {
>> +    struct resctrl_schema *s;
>>       struct rdt_resource *r;
>>       unsigned long fflags;
>>       char name[32];
>> @@ -1809,9 +1819,10 @@ static int rdtgroup_create_info_dir(struct kernfs_node *parent_kn)
>>       if (ret)
>>           goto out_destroy;
>>   -    for_each_alloc_enabled_rdt_resource(r) {
>> +    list_for_each_entry(s, &resctrl_all_schema, list) {
>> +        r = s->res;
>>           fflags =  r->fflags | RF_CTRL_INFO;
>> -        ret = rdtgroup_mkdir_info_resdir(r, r->name, fflags);
>> +        ret = rdtgroup_mkdir_info_resdir(s, r->name, fflags);
>>           if (ret)
>>               goto out_destroy;
>>       }

> I think it would be helpful to add a comment here to compensate for the symmetry that is
> removed ("for_each_alloc_enabled_rdt_resource()" followed by a
> "for_each_mon_enabled_rdt_resource()").

Sure, the thing to convey is the first loop is for 'alloc_enabled' controls.


Thanks,

James