When the cycles event isn't available evsel will fallback to the
cpu-clock software event. task-clock is similar to cpu-clock but only
runs when the process is running. Falling back to cpu-clock when not
system wide leads to confusion, by falling back to task-clock it is
hoped the confusion is less.
Pass the target to determine if task-clock is more appropriate. Update
a nearby comment and debug string for the change.
---
v2. Use target__has_cpu as suggested by Namhyung.
https://lpc.events/event/17/contributions/1556/
Signed-off-by: Ian Rogers <[email protected]>
---
tools/perf/builtin-record.c | 2 +-
tools/perf/builtin-stat.c | 2 +-
tools/perf/builtin-top.c | 2 +-
tools/perf/util/evsel.c | 18 ++++++++++--------
tools/perf/util/evsel.h | 3 ++-
5 files changed, 15 insertions(+), 12 deletions(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 8ec818568662..d8bb59511fdd 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1350,7 +1350,7 @@ static int record__open(struct record *rec)
evlist__for_each_entry(evlist, pos) {
try_again:
if (evsel__open(pos, pos->core.cpus, pos->core.threads) < 0) {
- if (evsel__fallback(pos, errno, msg, sizeof(msg))) {
+ if (evsel__fallback(pos, &opts->target, errno, msg, sizeof(msg))) {
if (verbose > 0)
ui__warning("%s\n", msg);
goto try_again;
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index a3af805a1d57..d8e5d6f7a87a 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -653,7 +653,7 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
if ((evsel__leader(counter) != counter) ||
!(counter->core.leader->nr_members > 1))
return COUNTER_SKIP;
- } else if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
+ } else if (evsel__fallback(counter, &target, errno, msg, sizeof(msg))) {
if (verbose > 0)
ui__warning("%s\n", msg);
return COUNTER_RETRY;
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index ea8c7eca5eee..1e42bd1c7d5a 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1044,7 +1044,7 @@ static int perf_top__start_counters(struct perf_top *top)
perf_top_overwrite_fallback(top, counter))
goto try_again;
- if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
+ if (evsel__fallback(counter, &opts->target, errno, msg, sizeof(msg))) {
if (verbose > 0)
ui__warning("%s\n", msg);
goto try_again;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index a5da74e3a517..532f34d9fcb5 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2853,7 +2853,8 @@ u64 evsel__intval_common(struct evsel *evsel, struct perf_sample *sample, const
#endif
-bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
+bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
+ char *msg, size_t msgsize)
{
int paranoid;
@@ -2861,18 +2862,19 @@ bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
evsel->core.attr.type == PERF_TYPE_HARDWARE &&
evsel->core.attr.config == PERF_COUNT_HW_CPU_CYCLES) {
/*
- * If it's cycles then fall back to hrtimer based
- * cpu-clock-tick sw counter, which is always available even if
- * no PMU support.
+ * If it's cycles then fall back to hrtimer based cpu-clock sw
+ * counter, which is always available even if no PMU support.
*
* PPC returns ENXIO until 2.6.37 (behavior changed with commit
* b0a873e).
*/
- scnprintf(msg, msgsize, "%s",
-"The cycles event is not supported, trying to fall back to cpu-clock-ticks");
-
evsel->core.attr.type = PERF_TYPE_SOFTWARE;
- evsel->core.attr.config = PERF_COUNT_SW_CPU_CLOCK;
+ evsel->core.attr.config = target__has_cpu(target)
+ ? PERF_COUNT_SW_CPU_CLOCK
+ : PERF_COUNT_SW_TASK_CLOCK;
+ scnprintf(msg, msgsize,
+ "The cycles event is not supported, trying to fall back to %s",
+ target__has_cpu(target) ? "cpu-clock" : "task-clock");
zfree(&evsel->name);
return true;
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index f19ac9f027ef..efbb6e848287 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -460,7 +460,8 @@ static inline bool evsel__is_clock(const struct evsel *evsel)
evsel__match(evsel, SOFTWARE, SW_TASK_CLOCK);
}
-bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize);
+bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
+ char *msg, size_t msgsize);
int evsel__open_strerror(struct evsel *evsel, struct target *target,
int err, char *msg, size_t size);
--
2.43.0.rc1.413.gea7ed67945-goog
On Mon, Nov 20, 2023 at 4:04 PM Ian Rogers <[email protected]> wrote:
>
> When the cycles event isn't available evsel will fallback to the
> cpu-clock software event. task-clock is similar to cpu-clock but only
> runs when the process is running. Falling back to cpu-clock when not
> system wide leads to confusion, by falling back to task-clock it is
> hoped the confusion is less.
>
> Pass the target to determine if task-clock is more appropriate. Update
> a nearby comment and debug string for the change.
>
> ---
> v2. Use target__has_cpu as suggested by Namhyung.
> https://lpc.events/event/17/contributions/1556/
>
> Signed-off-by: Ian Rogers <[email protected]>
Ping.
Thanks,
Ian
> ---
> tools/perf/builtin-record.c | 2 +-
> tools/perf/builtin-stat.c | 2 +-
> tools/perf/builtin-top.c | 2 +-
> tools/perf/util/evsel.c | 18 ++++++++++--------
> tools/perf/util/evsel.h | 3 ++-
> 5 files changed, 15 insertions(+), 12 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 8ec818568662..d8bb59511fdd 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1350,7 +1350,7 @@ static int record__open(struct record *rec)
> evlist__for_each_entry(evlist, pos) {
> try_again:
> if (evsel__open(pos, pos->core.cpus, pos->core.threads) < 0) {
> - if (evsel__fallback(pos, errno, msg, sizeof(msg))) {
> + if (evsel__fallback(pos, &opts->target, errno, msg, sizeof(msg))) {
> if (verbose > 0)
> ui__warning("%s\n", msg);
> goto try_again;
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index a3af805a1d57..d8e5d6f7a87a 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -653,7 +653,7 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
> if ((evsel__leader(counter) != counter) ||
> !(counter->core.leader->nr_members > 1))
> return COUNTER_SKIP;
> - } else if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
> + } else if (evsel__fallback(counter, &target, errno, msg, sizeof(msg))) {
> if (verbose > 0)
> ui__warning("%s\n", msg);
> return COUNTER_RETRY;
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index ea8c7eca5eee..1e42bd1c7d5a 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -1044,7 +1044,7 @@ static int perf_top__start_counters(struct perf_top *top)
> perf_top_overwrite_fallback(top, counter))
> goto try_again;
>
> - if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
> + if (evsel__fallback(counter, &opts->target, errno, msg, sizeof(msg))) {
> if (verbose > 0)
> ui__warning("%s\n", msg);
> goto try_again;
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index a5da74e3a517..532f34d9fcb5 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2853,7 +2853,8 @@ u64 evsel__intval_common(struct evsel *evsel, struct perf_sample *sample, const
>
> #endif
>
> -bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
> +bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
> + char *msg, size_t msgsize)
> {
> int paranoid;
>
> @@ -2861,18 +2862,19 @@ bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
> evsel->core.attr.type == PERF_TYPE_HARDWARE &&
> evsel->core.attr.config == PERF_COUNT_HW_CPU_CYCLES) {
> /*
> - * If it's cycles then fall back to hrtimer based
> - * cpu-clock-tick sw counter, which is always available even if
> - * no PMU support.
> + * If it's cycles then fall back to hrtimer based cpu-clock sw
> + * counter, which is always available even if no PMU support.
> *
> * PPC returns ENXIO until 2.6.37 (behavior changed with commit
> * b0a873e).
> */
> - scnprintf(msg, msgsize, "%s",
> -"The cycles event is not supported, trying to fall back to cpu-clock-ticks");
> -
> evsel->core.attr.type = PERF_TYPE_SOFTWARE;
> - evsel->core.attr.config = PERF_COUNT_SW_CPU_CLOCK;
> + evsel->core.attr.config = target__has_cpu(target)
> + ? PERF_COUNT_SW_CPU_CLOCK
> + : PERF_COUNT_SW_TASK_CLOCK;
> + scnprintf(msg, msgsize,
> + "The cycles event is not supported, trying to fall back to %s",
> + target__has_cpu(target) ? "cpu-clock" : "task-clock");
>
> zfree(&evsel->name);
> return true;
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index f19ac9f027ef..efbb6e848287 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -460,7 +460,8 @@ static inline bool evsel__is_clock(const struct evsel *evsel)
> evsel__match(evsel, SOFTWARE, SW_TASK_CLOCK);
> }
>
> -bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize);
> +bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
> + char *msg, size_t msgsize);
> int evsel__open_strerror(struct evsel *evsel, struct target *target,
> int err, char *msg, size_t size);
>
> --
> 2.43.0.rc1.413.gea7ed67945-goog
>
On Mon, Dec 4, 2023 at 8:02 AM Ian Rogers <[email protected]> wrote:
>
> On Mon, Nov 20, 2023 at 4:04 PM Ian Rogers <[email protected]> wrote:
> >
> > When the cycles event isn't available evsel will fallback to the
> > cpu-clock software event. task-clock is similar to cpu-clock but only
> > runs when the process is running. Falling back to cpu-clock when not
> > system wide leads to confusion, by falling back to task-clock it is
> > hoped the confusion is less.
> >
> > Pass the target to determine if task-clock is more appropriate. Update
> > a nearby comment and debug string for the change.
> >
> > ---
> > v2. Use target__has_cpu as suggested by Namhyung.
> > https://lpc.events/event/17/contributions/1556/
> >
> > Signed-off-by: Ian Rogers <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Thanks,
Namhyung
> On 21-Nov-2023, at 5:34 AM, Ian Rogers <[email protected]> wrote:
>
> When the cycles event isn't available evsel will fallback to the
> cpu-clock software event. task-clock is similar to cpu-clock but only
> runs when the process is running. Falling back to cpu-clock when not
> system wide leads to confusion, by falling back to task-clock it is
> hoped the confusion is less.
>
> Pass the target to determine if task-clock is more appropriate. Update
> a nearby comment and debug string for the change.
>
> ---
> v2. Use target__has_cpu as suggested by Namhyung.
> https://lpc.events/event/17/contributions/1556/
>
> Signed-off-by: Ian Rogers <[email protected]>
> ---
> tools/perf/builtin-record.c | 2 +-
> tools/perf/builtin-stat.c | 2 +-
> tools/perf/builtin-top.c | 2 +-
> tools/perf/util/evsel.c | 18 ++++++++++--------
> tools/perf/util/evsel.h | 3 ++-
> 5 files changed, 15 insertions(+), 12 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 8ec818568662..d8bb59511fdd 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1350,7 +1350,7 @@ static int record__open(struct record *rec)
> evlist__for_each_entry(evlist, pos) {
> try_again:
> if (evsel__open(pos, pos->core.cpus, pos->core.threads) < 0) {
> - if (evsel__fallback(pos, errno, msg, sizeof(msg))) {
> + if (evsel__fallback(pos, &opts->target, errno, msg, sizeof(msg))) {
Hi Ian
Tested this with perf record and I could find the code fallback to using task-clock
./perf record -v ls
Warning:
The cycles event is not supported, trying to fall back to task-clock
But in case of “perf stat”, in my environment, found that the code path won't invoke “evsel__fallback”.
Snippet for builtin-stat.c
if (errno == EINVAL || errno == ENOSYS ||
errno == ENOENT || errno == EOPNOTSUPP ||
errno == ENXIO) {
if (verbose > 0)
ui__warning("%s event is not supported by the kernel.\n",
evsel__name(counter));
counter->supported = false;
/*
* errored is a sticky flag that means one of the counter's
* cpu event had a problem and needs to be reexamined.
*/
counter->errored = true;
if ((evsel__leader(counter) != counter) ||
!(counter->core.leader->nr_members > 1))
return COUNTER_SKIP;
} else if (evsel__fallback(counter, &target, errno, msg, sizeof(msg))) {
if (verbose > 0)
ui__warning("%s\n", msg);
return COUNTER_RETRY;
So if the perf_event_open returns ENOENT, we won’t do a fallback in builtin-stat.c
Should we address cycles differently here ? Any comments ?
Thanks
Athira
>
> if (verbose > 0)
> ui__warning("%s\n", msg);
> goto try_again;
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index a3af805a1d57..d8e5d6f7a87a 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -653,7 +653,7 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
> if ((evsel__leader(counter) != counter) ||
> !(counter->core.leader->nr_members > 1))
> return COUNTER_SKIP;
> - } else if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
> + } else if (evsel__fallback(counter, &target, errno, msg, sizeof(msg))) {
> if (verbose > 0)
> ui__warning("%s\n", msg);
> return COUNTER_RETRY;
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index ea8c7eca5eee..1e42bd1c7d5a 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -1044,7 +1044,7 @@ static int perf_top__start_counters(struct perf_top *top)
> perf_top_overwrite_fallback(top, counter))
> goto try_again;
>
> - if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
> + if (evsel__fallback(counter, &opts->target, errno, msg, sizeof(msg))) {
> if (verbose > 0)
> ui__warning("%s\n", msg);
> goto try_again;
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index a5da74e3a517..532f34d9fcb5 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2853,7 +2853,8 @@ u64 evsel__intval_common(struct evsel *evsel, struct perf_sample *sample, const
>
> #endif
>
> -bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
> +bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
> + char *msg, size_t msgsize)
> {
> int paranoid;
>
> @@ -2861,18 +2862,19 @@ bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
> evsel->core.attr.type == PERF_TYPE_HARDWARE &&
> evsel->core.attr.config == PERF_COUNT_HW_CPU_CYCLES) {
> /*
> - * If it's cycles then fall back to hrtimer based
> - * cpu-clock-tick sw counter, which is always available even if
> - * no PMU support.
> + * If it's cycles then fall back to hrtimer based cpu-clock sw
> + * counter, which is always available even if no PMU support.
> *
> * PPC returns ENXIO until 2.6.37 (behavior changed with commit
> * b0a873e).
> */
> - scnprintf(msg, msgsize, "%s",
> -"The cycles event is not supported, trying to fall back to cpu-clock-ticks");
> -
> evsel->core.attr.type = PERF_TYPE_SOFTWARE;
> - evsel->core.attr.config = PERF_COUNT_SW_CPU_CLOCK;
> + evsel->core.attr.config = target__has_cpu(target)
> + ? PERF_COUNT_SW_CPU_CLOCK
> + : PERF_COUNT_SW_TASK_CLOCK;
> + scnprintf(msg, msgsize,
> + "The cycles event is not supported, trying to fall back to %s",
> + target__has_cpu(target) ? "cpu-clock" : "task-clock");
>
> zfree(&evsel->name);
> return true;
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index f19ac9f027ef..efbb6e848287 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -460,7 +460,8 @@ static inline bool evsel__is_clock(const struct evsel *evsel)
> evsel__match(evsel, SOFTWARE, SW_TASK_CLOCK);
> }
>
> -bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize);
> +bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
> + char *msg, size_t msgsize);
> int evsel__open_strerror(struct evsel *evsel, struct target *target,
> int err, char *msg, size_t size);
>
> --
> 2.43.0.rc1.413.gea7ed67945-goog
>
Em Tue, Dec 05, 2023 at 04:51:01PM +0530, Athira Rajeev escreveu:
>
>
> > On 21-Nov-2023, at 5:34 AM, Ian Rogers <[email protected]> wrote:
> >
> > When the cycles event isn't available evsel will fallback to the
> > cpu-clock software event. task-clock is similar to cpu-clock but only
> > runs when the process is running. Falling back to cpu-clock when not
> > system wide leads to confusion, by falling back to task-clock it is
> > hoped the confusion is less.
> >
> > Pass the target to determine if task-clock is more appropriate. Update
> > a nearby comment and debug string for the change.
> >
> > ---
> > v2. Use target__has_cpu as suggested by Namhyung.
> > https://lpc.events/event/17/contributions/1556/
> >
> > Signed-off-by: Ian Rogers <[email protected]>
> > ---
> > tools/perf/builtin-record.c | 2 +-
> > tools/perf/builtin-stat.c | 2 +-
> > tools/perf/builtin-top.c | 2 +-
> > tools/perf/util/evsel.c | 18 ++++++++++--------
> > tools/perf/util/evsel.h | 3 ++-
> > 5 files changed, 15 insertions(+), 12 deletions(-)
> >
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index 8ec818568662..d8bb59511fdd 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -1350,7 +1350,7 @@ static int record__open(struct record *rec)
> > evlist__for_each_entry(evlist, pos) {
> > try_again:
> > if (evsel__open(pos, pos->core.cpus, pos->core.threads) < 0) {
> > - if (evsel__fallback(pos, errno, msg, sizeof(msg))) {
> > + if (evsel__fallback(pos, &opts->target, errno, msg, sizeof(msg))) {
>
> Hi Ian
>
> Tested this with perf record and I could find the code fallback to using task-clock
>
> ./perf record -v ls
> Warning:
> The cycles event is not supported, trying to fall back to task-clock
Ok, so I'll take that as a Tested-by: you, ok?
The "perf stat" part can be addressed in a follow up patch, when that
error handling is researched to remember why we have that ->supported,
->errored thing.
- Arnaldo
> But in case of “perf stat”, in my environment, found that the code path won't invoke “evsel__fallback”.
>
> Snippet for builtin-stat.c
> if (errno == EINVAL || errno == ENOSYS ||
> errno == ENOENT || errno == EOPNOTSUPP ||
> errno == ENXIO) {
> if (verbose > 0)
> ui__warning("%s event is not supported by the kernel.\n",
> evsel__name(counter));
> counter->supported = false;
> /*
> * errored is a sticky flag that means one of the counter's
> * cpu event had a problem and needs to be reexamined.
> */
> counter->errored = true;
>
> if ((evsel__leader(counter) != counter) ||
> !(counter->core.leader->nr_members > 1))
> return COUNTER_SKIP;
> } else if (evsel__fallback(counter, &target, errno, msg, sizeof(msg))) {
> if (verbose > 0)
> ui__warning("%s\n", msg);
> return COUNTER_RETRY;
>
> So if the perf_event_open returns ENOENT, we won’t do a fallback in builtin-stat.c
> Should we address cycles differently here ? Any comments ?
>
> Thanks
> Athira
> >
> > if (verbose > 0)
> > ui__warning("%s\n", msg);
> > goto try_again;
> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > index a3af805a1d57..d8e5d6f7a87a 100644
> > --- a/tools/perf/builtin-stat.c
> > +++ b/tools/perf/builtin-stat.c
> > @@ -653,7 +653,7 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
> > if ((evsel__leader(counter) != counter) ||
> > !(counter->core.leader->nr_members > 1))
> > return COUNTER_SKIP;
> > - } else if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
> > + } else if (evsel__fallback(counter, &target, errno, msg, sizeof(msg))) {
> > if (verbose > 0)
> > ui__warning("%s\n", msg);
> > return COUNTER_RETRY;
> > diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> > index ea8c7eca5eee..1e42bd1c7d5a 100644
> > --- a/tools/perf/builtin-top.c
> > +++ b/tools/perf/builtin-top.c
> > @@ -1044,7 +1044,7 @@ static int perf_top__start_counters(struct perf_top *top)
> > perf_top_overwrite_fallback(top, counter))
> > goto try_again;
> >
> > - if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
> > + if (evsel__fallback(counter, &opts->target, errno, msg, sizeof(msg))) {
> > if (verbose > 0)
> > ui__warning("%s\n", msg);
> > goto try_again;
> > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > index a5da74e3a517..532f34d9fcb5 100644
> > --- a/tools/perf/util/evsel.c
> > +++ b/tools/perf/util/evsel.c
> > @@ -2853,7 +2853,8 @@ u64 evsel__intval_common(struct evsel *evsel, struct perf_sample *sample, const
> >
> > #endif
> >
> > -bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
> > +bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
> > + char *msg, size_t msgsize)
> > {
> > int paranoid;
> >
> > @@ -2861,18 +2862,19 @@ bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
> > evsel->core.attr.type == PERF_TYPE_HARDWARE &&
> > evsel->core.attr.config == PERF_COUNT_HW_CPU_CYCLES) {
> > /*
> > - * If it's cycles then fall back to hrtimer based
> > - * cpu-clock-tick sw counter, which is always available even if
> > - * no PMU support.
> > + * If it's cycles then fall back to hrtimer based cpu-clock sw
> > + * counter, which is always available even if no PMU support.
> > *
> > * PPC returns ENXIO until 2.6.37 (behavior changed with commit
> > * b0a873e).
> > */
> > - scnprintf(msg, msgsize, "%s",
> > -"The cycles event is not supported, trying to fall back to cpu-clock-ticks");
> > -
> > evsel->core.attr.type = PERF_TYPE_SOFTWARE;
> > - evsel->core.attr.config = PERF_COUNT_SW_CPU_CLOCK;
> > + evsel->core.attr.config = target__has_cpu(target)
> > + ? PERF_COUNT_SW_CPU_CLOCK
> > + : PERF_COUNT_SW_TASK_CLOCK;
> > + scnprintf(msg, msgsize,
> > + "The cycles event is not supported, trying to fall back to %s",
> > + target__has_cpu(target) ? "cpu-clock" : "task-clock");
> >
> > zfree(&evsel->name);
> > return true;
> > diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> > index f19ac9f027ef..efbb6e848287 100644
> > --- a/tools/perf/util/evsel.h
> > +++ b/tools/perf/util/evsel.h
> > @@ -460,7 +460,8 @@ static inline bool evsel__is_clock(const struct evsel *evsel)
> > evsel__match(evsel, SOFTWARE, SW_TASK_CLOCK);
> > }
> >
> > -bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize);
> > +bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
> > + char *msg, size_t msgsize);
> > int evsel__open_strerror(struct evsel *evsel, struct target *target,
> > int err, char *msg, size_t size);
> >
> > --
> > 2.43.0.rc1.413.gea7ed67945-goog
> >
>
--
- Arnaldo
> On 05-Dec-2023, at 8:55 PM, Arnaldo Carvalho de Melo <[email protected]> wrote:
>
> Em Tue, Dec 05, 2023 at 04:51:01PM +0530, Athira Rajeev escreveu:
>>
>>
>>> On 21-Nov-2023, at 5:34 AM, Ian Rogers <[email protected]> wrote:
>>>
>>> When the cycles event isn't available evsel will fallback to the
>>> cpu-clock software event. task-clock is similar to cpu-clock but only
>>> runs when the process is running. Falling back to cpu-clock when not
>>> system wide leads to confusion, by falling back to task-clock it is
>>> hoped the confusion is less.
>>>
>>> Pass the target to determine if task-clock is more appropriate. Update
>>> a nearby comment and debug string for the change.
>>>
>>> ---
>>> v2. Use target__has_cpu as suggested by Namhyung.
>>> https://lpc.events/event/17/contributions/1556/
>>>
>>> Signed-off-by: Ian Rogers <[email protected]>
>>> ---
>>> tools/perf/builtin-record.c | 2 +-
>>> tools/perf/builtin-stat.c | 2 +-
>>> tools/perf/builtin-top.c | 2 +-
>>> tools/perf/util/evsel.c | 18 ++++++++++--------
>>> tools/perf/util/evsel.h | 3 ++-
>>> 5 files changed, 15 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>>> index 8ec818568662..d8bb59511fdd 100644
>>> --- a/tools/perf/builtin-record.c
>>> +++ b/tools/perf/builtin-record.c
>>> @@ -1350,7 +1350,7 @@ static int record__open(struct record *rec)
>>> evlist__for_each_entry(evlist, pos) {
>>> try_again:
>>> if (evsel__open(pos, pos->core.cpus, pos->core.threads) < 0) {
>>> - if (evsel__fallback(pos, errno, msg, sizeof(msg))) {
>>> + if (evsel__fallback(pos, &opts->target, errno, msg, sizeof(msg))) {
>>
>> Hi Ian
>>
>> Tested this with perf record and I could find the code fallback to using task-clock
>>
>> ./perf record -v ls
>> Warning:
>> The cycles event is not supported, trying to fall back to task-clock
>
> Ok, so I'll take that as a Tested-by: you, ok?
Hi Arnaldo,
Please add my Tested-by.
Tested-by: Athira Rajeev <[email protected]>
>
> The "perf stat" part can be addressed in a follow up patch, when that
> error handling is researched to remember why we have that ->supported,
> ->errored thing.
Sure, I will take a look at why we have that difference in “perf stat”
Thanks
Athira
>
> - Arnaldo
>
>> But in case of “perf stat”, in my environment, found that the code path won't invoke “evsel__fallback”.
>>
>> Snippet for builtin-stat.c
>> if (errno == EINVAL || errno == ENOSYS ||
>> errno == ENOENT || errno == EOPNOTSUPP ||
>> errno == ENXIO) {
>> if (verbose > 0)
>> ui__warning("%s event is not supported by the kernel.\n",
>> evsel__name(counter));
>> counter->supported = false;
>> /*
>> * errored is a sticky flag that means one of the counter's
>> * cpu event had a problem and needs to be reexamined.
>> */
>> counter->errored = true;
>>
>> if ((evsel__leader(counter) != counter) ||
>> !(counter->core.leader->nr_members > 1))
>> return COUNTER_SKIP;
>> } else if (evsel__fallback(counter, &target, errno, msg, sizeof(msg))) {
>> if (verbose > 0)
>> ui__warning("%s\n", msg);
>> return COUNTER_RETRY;
>>
>> So if the perf_event_open returns ENOENT, we won’t do a fallback in builtin-stat.c
>> Should we address cycles differently here ? Any comments ?
>>
>> Thanks
>> Athira
>>>
>>> if (verbose > 0)
>>> ui__warning("%s\n", msg);
>>> goto try_again;
>>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>>> index a3af805a1d57..d8e5d6f7a87a 100644
>>> --- a/tools/perf/builtin-stat.c
>>> +++ b/tools/perf/builtin-stat.c
>>> @@ -653,7 +653,7 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
>>> if ((evsel__leader(counter) != counter) ||
>>> !(counter->core.leader->nr_members > 1))
>>> return COUNTER_SKIP;
>>> - } else if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
>>> + } else if (evsel__fallback(counter, &target, errno, msg, sizeof(msg))) {
>>> if (verbose > 0)
>>> ui__warning("%s\n", msg);
>>> return COUNTER_RETRY;
>>> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
>>> index ea8c7eca5eee..1e42bd1c7d5a 100644
>>> --- a/tools/perf/builtin-top.c
>>> +++ b/tools/perf/builtin-top.c
>>> @@ -1044,7 +1044,7 @@ static int perf_top__start_counters(struct perf_top *top)
>>> perf_top_overwrite_fallback(top, counter))
>>> goto try_again;
>>>
>>> - if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
>>> + if (evsel__fallback(counter, &opts->target, errno, msg, sizeof(msg))) {
>>> if (verbose > 0)
>>> ui__warning("%s\n", msg);
>>> goto try_again;
>>> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
>>> index a5da74e3a517..532f34d9fcb5 100644
>>> --- a/tools/perf/util/evsel.c
>>> +++ b/tools/perf/util/evsel.c
>>> @@ -2853,7 +2853,8 @@ u64 evsel__intval_common(struct evsel *evsel, struct perf_sample *sample, const
>>>
>>> #endif
>>>
>>> -bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
>>> +bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
>>> + char *msg, size_t msgsize)
>>> {
>>> int paranoid;
>>>
>>> @@ -2861,18 +2862,19 @@ bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
>>> evsel->core.attr.type == PERF_TYPE_HARDWARE &&
>>> evsel->core.attr.config == PERF_COUNT_HW_CPU_CYCLES) {
>>> /*
>>> - * If it's cycles then fall back to hrtimer based
>>> - * cpu-clock-tick sw counter, which is always available even if
>>> - * no PMU support.
>>> + * If it's cycles then fall back to hrtimer based cpu-clock sw
>>> + * counter, which is always available even if no PMU support.
>>> *
>>> * PPC returns ENXIO until 2.6.37 (behavior changed with commit
>>> * b0a873e).
>>> */
>>> - scnprintf(msg, msgsize, "%s",
>>> -"The cycles event is not supported, trying to fall back to cpu-clock-ticks");
>>> -
>>> evsel->core.attr.type = PERF_TYPE_SOFTWARE;
>>> - evsel->core.attr.config = PERF_COUNT_SW_CPU_CLOCK;
>>> + evsel->core.attr.config = target__has_cpu(target)
>>> + ? PERF_COUNT_SW_CPU_CLOCK
>>> + : PERF_COUNT_SW_TASK_CLOCK;
>>> + scnprintf(msg, msgsize,
>>> + "The cycles event is not supported, trying to fall back to %s",
>>> + target__has_cpu(target) ? "cpu-clock" : "task-clock");
>>>
>>> zfree(&evsel->name);
>>> return true;
>>> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
>>> index f19ac9f027ef..efbb6e848287 100644
>>> --- a/tools/perf/util/evsel.h
>>> +++ b/tools/perf/util/evsel.h
>>> @@ -460,7 +460,8 @@ static inline bool evsel__is_clock(const struct evsel *evsel)
>>> evsel__match(evsel, SOFTWARE, SW_TASK_CLOCK);
>>> }
>>>
>>> -bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize);
>>> +bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
>>> + char *msg, size_t msgsize);
>>> int evsel__open_strerror(struct evsel *evsel, struct target *target,
>>> int err, char *msg, size_t size);
>>>
>>> --
>>> 2.43.0.rc1.413.gea7ed67945-goog
>>>
>>
>
> --
>
> - Arnaldo