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Date: Sun, 14 Nov 2021 18:02:04 +0100
From: Jiri Olsa <jolsa@...hat.com>
To: Ian Rogers <irogers@...gle.com>
Cc: Andi Kleen <ak@...ux.intel.com>,
Namhyung Kim <namhyung@...nel.org>,
John Garry <john.garry@...wei.com>,
Kajol Jain <kjain@...ux.ibm.com>,
"Paul A . Clarke" <pc@...ibm.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Riccardo Mancini <rickyman7@...il.com>,
Kan Liang <kan.liang@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
eranian@...gle.com
Subject: Re: [PATCH 2/2] perf parse-events: Architecture specific leader
override
On Fri, Nov 12, 2021 at 11:15:48PM -0800, Ian Rogers wrote:
> Currently topdown events must appear after a slots event:
>
> $ perf stat -e '{slots,topdown-fe-bound}' /bin/true
>
> Performance counter stats for '/bin/true':
>
> 3,183,090 slots
> 986,133 topdown-fe-bound
>
> Reversing the events yields:
>
> $ perf stat -e '{topdown-fe-bound,slots}' /bin/true
> Error:
> The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (topdown-fe-bound).
why is this actually failing?
>
> For metrics the order of events is determined by iterating over a
> hashmap, and so slots isn't guaranteed to be first which can yield this
> error.
>
> Change the set_leader in parse-events, called when a group is closed, so
> that rather than always making the first event the leader, if the slots
> event exists then it is made the leader. It is then moved to the head of
> the evlist otherwise it won't be opened in the correct order.
>
> The result is:
>
> $ perf stat -e '{topdown-fe-bound,slots}' /bin/true
>
> Performance counter stats for '/bin/true':
>
> 3,274,795 slots
> 1,001,702 topdown-fe-bound
>
> A problem with this approach is the slots event is identified by name,
> names can be overwritten like 'cpu/slots,name=foo/' and this causes the
> leader change to fail.
would it be better then to move this shuffle to the metric code directly,
and make sure it only spits 'good' order of events?
and keep "-e '{topdown-fe-bound,slots}'" to fail if user specifies that on
the command line
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
> tools/perf/arch/x86/util/evlist.c | 17 +++++++++++++++++
> tools/perf/util/evlist.h | 1 +
> tools/perf/util/parse-events.c | 16 +++++++++++-----
> tools/perf/util/parse-events.h | 4 ++--
> tools/perf/util/parse-events.y | 12 ++++++++----
> 5 files changed, 39 insertions(+), 11 deletions(-)
>
> diff --git a/tools/perf/arch/x86/util/evlist.c b/tools/perf/arch/x86/util/evlist.c
> index 0b0951030a2f..1624372b2da2 100644
> --- a/tools/perf/arch/x86/util/evlist.c
> +++ b/tools/perf/arch/x86/util/evlist.c
> @@ -17,3 +17,20 @@ int arch_evlist__add_default_attrs(struct evlist *evlist)
> else
> return parse_events(evlist, TOPDOWN_L1_EVENTS, NULL);
> }
> +
> +struct evsel *arch_evlist__leader(struct list_head *list)
> +{
> + struct evsel *evsel, *first;
> +
> + first = list_entry(list->next, struct evsel, core.node);
> +
> + if (!pmu_have_event("cpu", "slots"))
> + return first;
> +
> + __evlist__for_each_entry(list, evsel) {
> + if (evsel->pmu_name && !strcmp(evsel->pmu_name, "cpu") &&
> + evsel->name && strstr(evsel->name, "slots"))
> + return evsel;
> + }
> + return first;
> +}
> diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
> index 97bfb8d0be4f..993437ffe429 100644
> --- a/tools/perf/util/evlist.h
> +++ b/tools/perf/util/evlist.h
> @@ -110,6 +110,7 @@ int __evlist__add_default_attrs(struct evlist *evlist,
> __evlist__add_default_attrs(evlist, array, ARRAY_SIZE(array))
>
> int arch_evlist__add_default_attrs(struct evlist *evlist);
> +struct evsel *arch_evlist__leader(struct list_head *list);
>
> int evlist__add_dummy(struct evlist *evlist);
>
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 6308ba739d19..a2f4c086986f 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1821,22 +1821,28 @@ parse_events__set_leader_for_uncore_aliase(char *name, struct list_head *list,
> return ret;
> }
>
> -void parse_events__set_leader(char *name, struct list_head *list,
> - struct parse_events_state *parse_state)
> +__weak struct evsel *arch_evlist__leader(struct list_head *list)
> +{
> + return list_entry(list->next, struct evsel, core.node);
> +}
> +
> +struct list_head *parse_events__set_leader(char *name, struct list_head *list,
> + struct parse_events_state *parse_state)
> {
> struct evsel *leader;
>
> if (list_empty(list)) {
> WARN_ONCE(true, "WARNING: failed to set leader: empty list");
> - return;
> + return NULL;
> }
>
> if (parse_events__set_leader_for_uncore_aliase(name, list, parse_state))
> - return;
> + return NULL;
>
> - leader = list_entry(list->next, struct evsel, core.node);
> + leader = arch_evlist__leader(list);
> __perf_evlist__set_leader(list, &leader->core);
> leader->group_name = name ? strdup(name) : NULL;
> + return &leader->core.node;
> }
>
> /* list_event is assumed to point to malloc'ed memory */
> diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
> index c7fc93f54577..8a6e6b4d5cbe 100644
> --- a/tools/perf/util/parse-events.h
> +++ b/tools/perf/util/parse-events.h
> @@ -211,8 +211,8 @@ int parse_events_copy_term_list(struct list_head *old,
>
> enum perf_pmu_event_symbol_type
> perf_pmu__parse_check(const char *name);
> -void parse_events__set_leader(char *name, struct list_head *list,
> - struct parse_events_state *parse_state);
> +struct list_head *parse_events__set_leader(char *name, struct list_head *list,
> + struct parse_events_state *parse_state);
> void parse_events_update_lists(struct list_head *list_event,
> struct list_head *list_all);
> void parse_events_evlist_error(struct parse_events_state *parse_state,
> diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> index 174158982fae..5358c400f938 100644
> --- a/tools/perf/util/parse-events.y
> +++ b/tools/perf/util/parse-events.y
> @@ -199,20 +199,24 @@ group_def
> group_def:
> PE_NAME '{' events '}'
> {
> - struct list_head *list = $3;
> + struct list_head *new_head, *list = $3;
>
> inc_group_count(list, _parse_state);
> - parse_events__set_leader($1, list, _parse_state);
> + new_head = parse_events__set_leader($1, list, _parse_state);
> + if (new_head)
> + list_move(new_head, list);
why not put these last 2 lines to parse_events__set_leader as well?
> free($1);
> $$ = list;
> }
> |
> '{' events '}'
> {
> - struct list_head *list = $2;
> + struct list_head *new_head, *list = $2;
>
> inc_group_count(list, _parse_state);
> - parse_events__set_leader(NULL, list, _parse_state);
> + new_head = parse_events__set_leader(NULL, list, _parse_state);
> + if (new_head)
> + list_move(new_head, list);
same
thanks,
jirka
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