linux-kernel - Re: [PATCH v3 12/27] perf parse-events: Support no alias assigned event inside hybrid PMU

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Message-ID: <7773d38a-4e1a-a610-367d-094f099d209d@linux.intel.com>
Date:   Thu, 15 Apr 2021 22:53:33 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v3 12/27] perf parse-events: Support no alias assigned
 event inside hybrid PMU

Hi Jiri,

On 4/15/2021 10:11 PM, Jiri Olsa wrote:
> On Thu, Apr 15, 2021 at 09:36:16PM +0800, Jin, Yao wrote:
> 
> SNIP
> 
>>>> +	int n = 0;
>>>> +
>>>> +	list_for_each(pos, list)
>>>> +		n++;
>>>> +
>>>> +	return n;
>>>> +}
>>>> +
>>>> +static int parse_events__with_hybrid_pmu(struct parse_events_state *parse_state,
>>>> +					 const char *str, char *pmu_name,
>>>> +					 bool *found, struct list_head *list)
>>>> +{
>>>> +	struct parse_events_state ps = {
>>>> +		.list           = LIST_HEAD_INIT(ps.list),
>>>> +		.stoken         = PE_START_EVENTS,
>>>> +		.pmu_name       = pmu_name,
>>>> +		.idx            = parse_state->idx,
>>>> +	};
>>>
>>> could we add this pmu_name directly to __parse_events?
>>>
>>
>> Do you suggest we directly call __parse_events()?
>>
>> int __parse_events(struct evlist *evlist, const char *str,
>> 		   struct parse_events_error *err, struct perf_pmu *fake_pmu)
>>
>> 	struct parse_events_state parse_state = {
>> 		.list	  = LIST_HEAD_INIT(parse_state.list),
>> 		.idx	  = evlist->core.nr_entries,
>> 		.error	  = err,
>> 		.evlist	  = evlist,
>> 		.stoken	  = PE_START_EVENTS,
>> 		.fake_pmu = fake_pmu,
>> 	};
>>
>> But for parse_events__with_hybrid_pmu, we don't have valid evlist. So if we
>> switch to __parse_events, evlist processing may be a problem.
> 
> you should use parse_state->evlist no? but we can chec/make this
> change in next itaration.. it's already lot of changes
> 
> jirka
> 

With my current code,

static int parse_events__with_hybrid_pmu(struct parse_events_state *parse_state,
					 const char *str, char *pmu_name,
					 struct list_head *list)
{
	struct parse_events_state ps = {
		.list           = LIST_HEAD_INIT(ps.list),
		.stoken         = PE_START_EVENTS,
		.pmu_name       = pmu_name,
		.idx            = parse_state->idx,
	};
	int ret;

	ret = parse_events__scanner(str, &ps);
	perf_pmu__parse_cleanup();

	if (!ret) {
		if (!list_empty(&ps.list)) {
			list_splice(&ps.list, list);
			parse_state->idx = ps.idx;
		}
	}

	return ret;
}

The new created evsels are added to the tail of list (ps.list) and ps.list is joined to the list 
(the parameter 'list').

If we want to reuse the __parse_events(), we may need to:

struct evlist *evlist = evlist__new();

__parse_events(evlist, str, NULL, NULL);
Add the evsels in evlist to the tail of list (the parameter 'list')
evlist__delete(evlist);

Is my understanding correct?

Yes, we have to change the interface of __parse_events() by adding a new parameter 'pmu_name', which 
will bring much more changes. I agree to make this change in follow-up patches.

Thanks
Jin Yao