Re: [PATCH 2/9] perf tools: Support the auxiliary event

Arnaldo Carvalho de Melo
2021-02-03T20:03:43Z

Em Tue, Feb 02, 2021 at 12:09:06PM -0800, kan.liang@linux.intel.com escreveu:
> From: Kan Liang <kan.liang@linux.intel.com>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index c26ea822..c48f6de 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2689,6 +2689,9 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
> if (perf_missing_features.aux_output)
> return scnprintf(msg, size, "The 'aux_output' feature is not supported, update the kernel.");
> break;
> + case ENODATA:
> + return scnprintf(msg, size, "Cannot collect data source with the load latency event alone. "
> + "Please add an auxiliary event in front of the load latency event.");

Are you sure this is the only case where ENODATA comes out from
perf_event_open()? Well, according to your comment in:

61b985e3e775a3a7 ("perf/x86/intel: Add perf core PMU support for Sapphire Rapids")

It should be at that point in time, so its safe to merge as-is, but then
I think this is fragile, what if someone else, in the future, not
knowing that ENODATA is supposed to be used only with that ancient CPU,
Sapphire Rapids, uses it? :-)

Please consider adding a check before assuming ENODATA is for this
specific case.

Back to processing the other patches.

- Arnaldo

> default:
> break;
> }
> diff --git a/tools/perf/util/mem-events.c b/tools/perf/util/mem-events.c
> index 19007e4..3edfb88 100644
> --- a/tools/perf/util/mem-events.c
> +++ b/tools/perf/util/mem-events.c
> @@ -56,6 +56,11 @@ char * __weak perf_mem_events__name(int i)
> return (char *)e->name;
> }
>
> +__weak bool is_mem_loads_aux_event(struct evsel *leader __maybe_unused)
> +{
> + return false;
> +}
> +
> int perf_mem_events__parse(const char *str)
> {
> char *tok, *saveptr = NULL;
> diff --git a/tools/perf/util/mem-events.h b/tools/perf/util/mem-events.h
> index 5ef1782..045a507 100644
> --- a/tools/perf/util/mem-events.h
> +++ b/tools/perf/util/mem-events.h
> @@ -9,6 +9,7 @@
> #include <linux/refcount.h>
> #include <linux/perf_event.h>
> #include "stat.h"
> +#include "evsel.h"
>
> struct perf_mem_event {
> bool record;
> @@ -39,6 +40,7 @@ int perf_mem_events__init(void);
>
> char *perf_mem_events__name(int i);
> struct perf_mem_event *perf_mem_events__ptr(int i);
> +bool is_mem_loads_aux_event(struct evsel *leader);
>
> void perf_mem_events__list(void);
>
> diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
> index 9db5097..0b36285 100644
> --- a/tools/perf/util/parse-events.l
> +++ b/tools/perf/util/parse-events.l
> @@ -356,6 +356,7 @@ bpf-output { return sym(yyscanner, PERF_TYPE_SOFTWARE, PERF_COUNT_SW_BPF_OUT
> cycles-ct |
> cycles-t |
> mem-loads |
> +mem-loads-aux |
> mem-stores |
> topdown-[a-z-]+ |
> tx-capacity-[a-z-]+ |
> diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
> index e70c9dd..d0735fb 100644
> --- a/tools/perf/util/record.c
> +++ b/tools/perf/util/record.c
> @@ -15,6 +15,8 @@
> #include "record.h"
> #include "../perf-sys.h"
> #include "topdown.h"
> +#include "map_symbol.h"
> +#include "mem-events.h"
>
> /*
> * evsel__config_leader_sampling() uses special rules for leader sampling.
> @@ -25,7 +27,8 @@ static struct evsel *evsel__read_sampler(struct evsel *evsel, struct evlist *evl
> {
> struct evsel *leader = evsel->leader;
>
> - if (evsel__is_aux_event(leader) || arch_topdown_sample_read(leader)) {
> + if (evsel__is_aux_event(leader) || arch_topdown_sample_read(leader) ||
> + is_mem_loads_aux_event(leader)) {
> evlist__for_each_entry(evlist, evsel) {
> if (evsel->leader == leader && evsel != evsel->leader)
> return evsel;
> --
> 2.7.4
>

--

- Arnaldo