linux-kernel - Re: [PATCH v8 17/25] x86/resctrl: Add the interface to assign/update counter assignment

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Message-ID: <2ceed0db-0c23-2902-30dc-eb0dcea0c667@amd.com>
Date: Mon, 21 Oct 2024 20:15:48 -0500
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, babu.moger@....com,
 corbet@....net, fenghua.yu@...el.com, tglx@...utronix.de, mingo@...hat.com,
 bp@...en8.de, dave.hansen@...ux.intel.com
Cc: x86@...nel.org, hpa@...or.com, paulmck@...nel.org, rdunlap@...radead.org,
 tj@...nel.org, peterz@...radead.org, yanjiewtw@...il.com,
 kim.phillips@....com, lukas.bulwahn@...il.com, seanjc@...gle.com,
 jmattson@...gle.com, leitao@...ian.org, jpoimboe@...nel.org,
 rick.p.edgecombe@...el.com, kirill.shutemov@...ux.intel.com,
 jithu.joseph@...el.com, kai.huang@...el.com, kan.liang@...ux.intel.com,
 daniel.sneddon@...ux.intel.com, pbonzini@...hat.com, sandipan.das@....com,
 ilpo.jarvinen@...ux.intel.com, peternewman@...gle.com,
 maciej.wieczor-retman@...el.com, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, eranian@...gle.com, james.morse@....com
Subject: Re: [PATCH v8 17/25] x86/resctrl: Add the interface to assign/update
 counter assignment

Hi Reinette,

On 10/21/2024 10:31 AM, Reinette Chatre wrote:
> Hi Babu,
> 
> On 10/21/24 7:40 AM, Moger, Babu wrote:
>> On 10/18/24 10:59, Reinette Chatre wrote:
>>> On 10/17/24 3:56 PM, Moger, Babu wrote:
>>>> On 10/15/2024 10:25 PM, Reinette Chatre wrote:
>>>>> On 10/9/24 10:39 AM, Babu Moger wrote:
>>>
>>>>>> + */
>>>>>> +int rdtgroup_assign_cntr_event(struct rdt_resource *r, struct rdtgroup *rdtgrp,
>>>>>> +                   struct rdt_mon_domain *d, enum resctrl_event_id evtid)
>>>>>> +{
>>>>>> +    int index = MBM_EVENT_ARRAY_INDEX(evtid);
>>>>>> +    int cntr_id = rdtgrp->mon.cntr_id[index];
>>>>>> +    int ret;
>>>>>> +
>>>>>> +    /*
>>>>>> +     * Allocate a new counter id to the event if the counter is not
>>>>>> +     * assigned already.
>>>>>> +     */
>>>>>> +    if (cntr_id == MON_CNTR_UNSET) {
>>>>>> +        cntr_id = mbm_cntr_alloc(r);
>>>>>> +        if (cntr_id < 0) {
>>>>>> +            rdt_last_cmd_puts("Out of MBM assignable counters\n");
>>>>>> +            return -ENOSPC;
>>>>>> +        }
>>>>>> +        rdtgrp->mon.cntr_id[index] = cntr_id;
>>>>>> +    }
>>>>>> +
>>>>>> +    if (!d) {
>>>>>> +        list_for_each_entry(d, &r->mon_domains, hdr.list) {
>>>>>> +            ret = resctrl_arch_config_cntr(r, d, evtid, rdtgrp->mon.rmid,
>>>>>> +                               rdtgrp->closid, cntr_id, true);
>>>>>> +            if (ret)
>>>>>> +                goto out_done_assign;
>>>>>> +
>>>>>> +            set_bit(cntr_id, d->mbm_cntr_map);
>>>>>
>>>>> The code pattern above is repeated four times in this work, twice in
>>>>> rdtgroup_assign_cntr_event() and twice in rdtgroup_unassign_cntr_event(). This
>>>>> duplication should be avoided. It can be done in a function that also resets
>>>>> the architectural state.
>>>>
>>>> Are you suggesting to combine rdtgroup_assign_cntr_event() and rdtgroup_unassign_cntr_event()?
>>>
>>> No. My comment was about the following pattern that is repeated four times:
>>> 	...
>>> 	ret = resctrl_arch_config_cntr(...)
>>> 	if (ret)
>>> 		...
>>> 	set_bit()/clear_bit()
>>> 	...
>>>
>>
>> ok.
>>
>>
>>>> It can be done. We need a flag to tell if it is a assign or unassign.
>>>
>>> There is already a flag that is used by resctrl_arch_config_cntr(), the same parameters
>>> as resctrl_arch_config_cntr() can be used for a wrapper that just calls
>>> resctrl_arch_config_cntr() directly and uses that same flag to
>>> select between set_bit() and clear_bit(). This wrapper can then also include
>>> the reset of architectural state.
>>
>> ok. Got it, It will look like this.
>>
>>
>> +/*
>> + * Wrapper to configure the counter in a domain.
>> + */
> 
> Please replace comment with a description of what the function does.

sure.

> 
>> +static int rdtgroup_config_cntr(struct rdt_resource *r,struct
> 
> While it keeps being a challenge to get naming right I do think this
> can start by replacing "rdtgroup" with "resctrl" (specifically,
> "rdtgroup_config_cntr() -> resctrl_config_cntr()") because, as seen
> with the parameters passed, this has nothing to do with rdtgroup.

Sure.

> 
>> rdt_mon_domain *d,
>> +                               enum resctrl_event_id evtid, u32 rmid, u32
>> closid,
>> +                               u32 cntr_id, bool assign)
>> +{
>> +       int ret;
>> +
>> +       ret = resctrl_arch_config_cntr(r, d, evtid, rmid, closid, cntr_id,
>> assign);
>> +       if (ret)
>> +               return ret;
>> +
>> +       if (assign)
>> +               __set_bit(cntr_id, d->mbm_cntr_map);
>> +       else
>> +               __clear_bit(cntr_id, d->mbm_cntr_map);
>> +
>> +       /*
>> +        * Reset the architectural state so that reading of hardware
>> +        * counter is not considered as an overflow in next update.
>> +        */
>> +       resctrl_arch_reset_rmid(r, d, closid, rmid, evtid);
>> +
>> +       return ret;
>> +}
>> +
> 
> Yes, this looks good. Thank you.
> 

Thanks-
- Babu Moger