Re: [PATCH v8 06/10] fs/resctrl: Add user interface to enable/disable io_alloc feature

[Reinette Chatre <reinette.chatre@intel.com>]

Hi Babu,

On 8/27/25 1:39 PM, Moger, Babu wrote:
> On 8/22/25 17:53, Moger, Babu wrote:
>> On 8/7/2025 8:49 PM, Reinette Chatre wrote:
>>> On 8/5/25 4:30 PM, Babu Moger wrote:

>>>
>>>> +    enum resctrl_conf_type peer_type;
>>>> +    struct resctrl_schema *peer_s;
>>>> +    int ret;
>>>> +
>>>> +    rdt_staged_configs_clear();
>>>> +
>>>> +    ret = rdtgroup_init_cat(s, closid);
>>>> +    if (ret < 0)
>>>> +        goto out;
>>>> +
>>>> +    /* Initialize schema for both CDP_DATA and CDP_CODE when CDP is
>>>> enabled */
>>>> +    if (resctrl_arch_get_cdp_enabled(r->rid)) {
>>>> +        peer_type = resctrl_peer_type(s->conf_type);
>>>> +        peer_s = resctrl_get_schema(peer_type);
>>>> +        if (peer_s) {
>>>> +            ret = rdtgroup_init_cat(peer_s, closid);
>>> This is unexpected. In v7 I suggested that when parsing the CBM of one
>>> of the CDP
>>> resources it is not necessary to do so again for the peer. The CBM can be
>>> parsed *once* and the configuration just copied over. See:
>>> https://lore.kernel.org/
>>> lkml/82045638-2b26-4682-9374-1c3e400a580a@intel.com/
>>
>> Let met try to understand.
>>
>> So, rdtgroup_init_cat() sets up the staged _config for the specific CDP
>> type for all the domains.
>>
>> We need to apply those staged_configs to its peer type on all the domains.

To put it more directly, this implementation keeps the CBM of CDP_CODE and
CDP_DATA in sync. Skipping the unnecessary and duplicate parsing and instead
copying the CBM from one to the other makes that obvious.

>>
>> Something like this?
>>
>> /* Initialize staged_config of the peer type when CDP is enabled */
>>         if (resctrl_arch_get_cdp_enabled(r->rid)) {
>>                 list_for_each_entry(d, &s->res->ctrl_domains, hdr.list) {
>>                         cfg = &d->staged_config[s->conf_type];
>>                         cfg_peer = &d->staged_config[peer_type];
>>                         cfg_peer->new_ctrl = cfg->new_ctrl;
>>                         cfg_peer->have_new_ctrl = cfg->have_new_ctrl;
>>                 }
>>         }
>>
> 
> Replaced with following snippet.
> 
> /* Initialize schema for both CDP_DATA and CDP_CODE when CDP is enabled */

Could this be more specific? For example,
"Keep CDP_CODE and CDP_DATA of io_alloc CLOSID's CBM in sync."

> +	if (resctrl_arch_get_cdp_enabled(r->rid)) {
> +		peer_type = resctrl_peer_type(s->conf_type);
> +		list_for_each_entry(d, &s->res->ctrl_domains, hdr.list)
> +			memcpy(&d->staged_config[peer_type],
> +			       &d->staged_config[s->conf_type],
> +			       sizeof(*d->staged_config));

This looks good to me. To make it obvious what types are dealt with this
can instead use sizeof(d->staged_config[0]).

Thank you.

Reinette