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Message-ID: <CAP-5=fX+aSDLMDL3DMNCQ4tDuhaZPv-L6OgfOso3q5wf7anoGg@mail.gmail.com>
Date: Wed, 5 Mar 2025 13:40:32 -0800
From: Ian Rogers <irogers@...gle.com>
To: James Clark <james.clark@...aro.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>, Robin Murphy <robin.murphy@....com>,
Leo Yan <leo.yan@....com>, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] perf list: Collapse similar events across PMUs
On Tue, Mar 4, 2025 at 5:50 AM James Clark <james.clark@...aro.org> wrote:
>
> Instead of showing multiple line items with the same event name and
> description, show a single line and concatenate all PMUs that this
> event can belong to.
>
> Don't do it for json output. Machine readable output doesn't need to be
> minimized, and changing the "Unit" field to a list type would break
> backwards compatibility.
>
> Before:
> $ perf list -v
> ...
> br_indirect_spec
> [Branch speculatively executed,indirect branch. Unit: armv8_cortex_a53]
> br_indirect_spec
> [Branch speculatively executed,indirect branch. Unit: armv8_cortex_a57]
>
> After:
>
> $ perf list -v
> ...
> br_indirect_spec
> [Branch speculatively executed,indirect branch. Unit: armv8_cortex_a53,armv8_cortex_a57]
>
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---
> tools/perf/builtin-list.c | 2 ++
> tools/perf/util/pmus.c | 75 +++++++++++++++++++++++++++++++++++++-----
> tools/perf/util/print-events.h | 1 +
> 3 files changed, 70 insertions(+), 8 deletions(-)
>
> diff --git a/tools/perf/builtin-list.c b/tools/perf/builtin-list.c
> index fed482adb039..aacd7beae2a0 100644
> --- a/tools/perf/builtin-list.c
> +++ b/tools/perf/builtin-list.c
> @@ -516,6 +516,7 @@ int cmd_list(int argc, const char **argv)
> .print_event = default_print_event,
> .print_metric = default_print_metric,
> .skip_duplicate_pmus = default_skip_duplicate_pmus,
> + .collapse_events = true
So collapse_events is put in the callbacks but isn't a callback. I
think skipping duplicates and collapsing are the same thing, I'd
prefer it if there weren't two terms for the same thing. If you prefer
collapsing as a name then default_skip_duplicate_pmus can be
default_collapse_pmus.
> };
> const char *cputype = NULL;
> const char *unit_name = NULL;
> @@ -574,6 +575,7 @@ int cmd_list(int argc, const char **argv)
> .print_event = json_print_event,
> .print_metric = json_print_metric,
> .skip_duplicate_pmus = json_skip_duplicate_pmus,
> + .collapse_events = false
> };
> ps = &json_ps;
> } else {
> diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
> index 4d60bac2d2b9..cb1b14ade25b 100644
> --- a/tools/perf/util/pmus.c
> +++ b/tools/perf/util/pmus.c
> @@ -453,17 +453,50 @@ static int cmp_sevent(const void *a, const void *b)
> /* Order by PMU name. */
> if (as->pmu == bs->pmu)
> return 0;
> - return strcmp(as->pmu_name ?: "", bs->pmu_name ?: "");
> + ret = strcmp(as->pmu_name ?: "", bs->pmu_name ?: "");
> + if (ret)
> + return ret;
> +
> + /* Order by remaining displayed fields for purposes of deduplication later */
> + ret = strcmp(as->scale_unit ?: "", bs->scale_unit ?: "");
> + if (ret)
> + return ret;
> + ret = !!as->deprecated - !!bs->deprecated;
> + if (ret)
> + return ret;
> + ret = strcmp(as->desc ?: "", bs->desc ?: "");
> + if (ret)
> + return ret;
> + return strcmp(as->long_desc ?: "", bs->long_desc ?: "");
> }
>
> -static bool pmu_alias_is_duplicate(struct sevent *a, struct sevent *b)
> +enum dup_type {
> + UNIQUE,
> + DUPLICATE,
> + SAME_TEXT
> +};
> +
> +static enum dup_type pmu_alias_duplicate_type(struct sevent *a, struct sevent *b)
> {
> /* Different names -> never duplicates */
> if (strcmp(a->name ?: "//", b->name ?: "//"))
> - return false;
> + return UNIQUE;
> +
> + /* Duplicate PMU name and event name -> hide completely */
> + if (strcmp(a->pmu_name, b->pmu_name) == 0)
> + return DUPLICATE;
> +
> + /* Any other different display text -> not duplicate */
> + if (strcmp(a->topic ?: "", b->topic ?: "") ||
> + strcmp(a->scale_unit ?: "", b->scale_unit ?: "") ||
> + a->deprecated != b->deprecated ||
> + strcmp(a->desc ?: "", b->desc ?: "") ||
> + strcmp(a->long_desc ?: "", b->long_desc ?: "")) {
> + return UNIQUE;
> + }
>
> - /* Don't remove duplicates for different PMUs */
> - return strcmp(a->pmu_name, b->pmu_name) == 0;
> + /* Same display text but different PMU -> collapse */
> + return SAME_TEXT;
> }
>
> struct events_callback_state {
> @@ -501,6 +534,21 @@ static int perf_pmus__print_pmu_events__callback(void *vstate,
> return 0;
> }
>
> +static void concat_pmu_names(char *pmu_names, size_t size, const char *a, const char *b)
> +{
> + size_t len = strlen(pmu_names);
> + size_t added;
> +
> + if (len)
> + added = snprintf(pmu_names + len, size - len, ",%s", b);
> + else
> + added = snprintf(pmu_names, size, "%s,%s", a, b);
> +
> + /* Truncate with ... */
> + if (added > 0 && added + len >= size)
> + sprintf(pmu_names + size - 4, "...");
> +}
> +
> void perf_pmus__print_pmu_events(const struct print_callbacks *print_cb, void *print_state)
> {
> struct perf_pmu *pmu;
> @@ -510,6 +558,7 @@ void perf_pmus__print_pmu_events(const struct print_callbacks *print_cb, void *p
> struct events_callback_state state;
> bool skip_duplicate_pmus = print_cb->skip_duplicate_pmus(print_state);
> struct perf_pmu *(*scan_fn)(struct perf_pmu *);
> + char pmu_names[128] = {0};
>
> if (skip_duplicate_pmus)
> scan_fn = perf_pmus__scan_skip_duplicates;
> @@ -539,12 +588,21 @@ void perf_pmus__print_pmu_events(const struct print_callbacks *print_cb, void *p
> qsort(aliases, len, sizeof(struct sevent), cmp_sevent);
> for (int j = 0; j < len; j++) {
> /* Skip duplicates */
> - if (j < len - 1 && pmu_alias_is_duplicate(&aliases[j], &aliases[j + 1]))
> - goto free;
> + if (j < len - 1) {
> + enum dup_type dt = pmu_alias_duplicate_type(&aliases[j], &aliases[j + 1]);
> +
> + if (dt == DUPLICATE) {
> + goto free;
> + } else if (print_cb->collapse_events && dt == SAME_TEXT) {
> + concat_pmu_names(pmu_names, sizeof(pmu_names),
> + aliases[j].pmu_name, aliases[j+1].pmu_name);
> + goto free;
> + }
> + }
I think a label called 'free' is a little unfortunate given the
function called free.
When I did things with sevent I was bringing over previous `perf list`
code mainly so that the perf list output before and after the changes
was identical. I wonder if this logic would be better placed in the
callback like default_print_event which already maintains state
(last_topic) to optionally print different things. This may better
encapsulate the behavior rather than the logic being in the PMU code.
>
> print_cb->print_event(print_state,
> aliases[j].topic,
> - aliases[j].pmu_name,
> + pmu_names[0] ? pmu_names : aliases[j].pmu_name,
> aliases[j].name,
> aliases[j].alias,
> aliases[j].scale_unit,
> @@ -553,6 +611,7 @@ void perf_pmus__print_pmu_events(const struct print_callbacks *print_cb, void *p
> aliases[j].desc,
> aliases[j].long_desc,
> aliases[j].encoding_desc);
The encoding_desc will have a PMU with the suffix removed as per
skipping duplicates:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/pmu.c?h=perf-tools-next#n1954
So I think something like:
```
br_mis_pred_retired
[Instruction architecturally executed,mispredicted branch. Unit:
armv9_cortex_a510,armv9_cortex_a710]
```
Would have an encoding of `armv9_cortex_a510/.../` without the a710
encoding being present. That said, I'm not sure anyone cares :-)
Thanks,
Ian
> + pmu_names[0] = '\0';
> free:
> zfree(&aliases[j].name);
> zfree(&aliases[j].alias);
> diff --git a/tools/perf/util/print-events.h b/tools/perf/util/print-events.h
> index 445efa1636c1..e91f9f830a2a 100644
> --- a/tools/perf/util/print-events.h
> +++ b/tools/perf/util/print-events.h
> @@ -27,6 +27,7 @@ struct print_callbacks {
> const char *threshold,
> const char *unit);
> bool (*skip_duplicate_pmus)(void *print_state);
> + bool collapse_events;
> };
>
> /** Print all events, the default when no options are specified. */
>
> --
> 2.34.1
>
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