linux-kernel - Re: [PATCH v2 3/3] perf-stat: introduce config stat.bpf-counter-events

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Date:   Thu, 8 Apr 2021 16:39:33 +0000
From:   Song Liu <songliubraving@...com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     Song Liu <song@...nel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        "jolsa@...nel.org" <jolsa@...nel.org>
Subject: Re: [PATCH v2 3/3] perf-stat: introduce config
 stat.bpf-counter-events



> On Apr 8, 2021, at 4:47 AM, Jiri Olsa <jolsa@...hat.com> wrote:
> 
> On Tue, Apr 06, 2021 at 05:36:01PM -0700, Song Liu wrote:
>> Currently, to use BPF to aggregate perf event counters, the user uses
>> --bpf-counters option. Enable "use bpf by default" events with a config
>> option, stat.bpf-counter-events. This is limited to hardware events in
>> evsel__hw_names.
>> 
>> This also enables mixed BPF event and regular event in the same sesssion.
>> For example:
>> 
>>   perf config stat.bpf-counter-events=instructions
>>   perf stat -e instructions,cs
>> 
> 
> so if we are mixing events now, how about uing modifier for bpf counters,
> instead of configuring .perfconfig list we could use:
> 
>  perf stat -e instructions:b,cs
> 
> thoughts?
> 
> the change below adds 'b' modifier and sets 'evsel::bpf_counter',
> feel free to use it

I think we will need both 'b' modifier and .perfconfig configuration. 
For systems with BPF-managed perf events running in the background, 
.perfconfig makes sure perf-stat sessions will share PMCs with these 
background monitoring tools. 'b' modifier, on the other hand, is useful
when the user knows there is opportunity to share the PMCs. 

Does this make sense? 

Thanks,
Song

> 
> jirka
> 
> 
> ---
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index ca52581f1b17..c55e4e58d1dc 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -82,6 +82,7 @@ struct evsel {
> 		bool			auto_merge_stats;
> 		bool			collect_stat;
> 		bool			weak_group;
> +		bool			bpf_counter;
> 		int			bpf_fd;
> 		struct bpf_object	*bpf_obj;
> 	};
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 9ecb45bea948..b5850f1ea90b 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1801,6 +1801,7 @@ struct event_modifier {
> 	int pinned;
> 	int weak;
> 	int exclusive;
> +	int bpf_counter;
> };
> 
> static int get_event_modifier(struct event_modifier *mod, char *str,
> @@ -1821,6 +1822,7 @@ static int get_event_modifier(struct event_modifier *mod, char *str,
> 	int exclude = eu | ek | eh;
> 	int exclude_GH = evsel ? evsel->exclude_GH : 0;
> 	int weak = 0;
> +	int bpf_counter = 0;
> 
> 	memset(mod, 0, sizeof(*mod));
> 
> @@ -1864,6 +1866,8 @@ static int get_event_modifier(struct event_modifier *mod, char *str,
> 			exclusive = 1;
> 		} else if (*str == 'W') {
> 			weak = 1;
> +		} else if (*str == 'b') {
> +			bpf_counter = 1;
> 		} else
> 			break;
> 
> @@ -1895,6 +1899,7 @@ static int get_event_modifier(struct event_modifier *mod, char *str,
> 	mod->sample_read = sample_read;
> 	mod->pinned = pinned;
> 	mod->weak = weak;
> +	mod->bpf_counter = bpf_counter;
> 	mod->exclusive = exclusive;
> 
> 	return 0;
> @@ -1909,7 +1914,7 @@ static int check_modifier(char *str)
> 	char *p = str;
> 
> 	/* The sizeof includes 0 byte as well. */
> -	if (strlen(str) > (sizeof("ukhGHpppPSDIWe") - 1))
> +	if (strlen(str) > (sizeof("ukhGHpppPSDIWeb") - 1))
> 		return -1;
> 
> 	while (*p) {
> @@ -1950,6 +1955,7 @@ int parse_events__modifier_event(struct list_head *list, char *str, bool add)
> 		evsel->sample_read         = mod.sample_read;
> 		evsel->precise_max         = mod.precise_max;
> 		evsel->weak_group	   = mod.weak;
> +		evsel->bpf_counter         = mod.bpf_counter;
> 
> 		if (evsel__is_group_leader(evsel)) {
> 			evsel->core.attr.pinned = mod.pinned;
> diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
> index 0b36285a9435..fb8646cc3e83 100644
> --- a/tools/perf/util/parse-events.l
> +++ b/tools/perf/util/parse-events.l
> @@ -210,7 +210,7 @@ name_tag	[\'][a-zA-Z_*?\[\]][a-zA-Z0-9_*?\-,\.\[\]:=]*[\']
> name_minus	[a-zA-Z_*?][a-zA-Z0-9\-_*?.:]*
> drv_cfg_term	[a-zA-Z0-9_\.]+(=[a-zA-Z0-9_*?\.:]+)?
> /* If you add a modifier you need to update check_modifier() */
> -modifier_event	[ukhpPGHSDIWe]+
> +modifier_event	[ukhpPGHSDIWeb]+
> modifier_bp	[rwx]{1,3}
> 
> %%
>