Em Tue, Nov 29, 2016 at 12:58:48PM -0700, David Ahern escreveu:
> Arnaldo reported an unhelpful error message when running perf sched
> timehist on a file that did not contain sched tracepoints:
>
> [root@jouet ~]# perf sched timehist
> No trace sample to read. Did you call 'perf record -R'?
>
> [root@jouet ~]# perf evlist -v
> cycles:ppp: size: 112, { sample_period, sample_freq }: 4000, sample_type:
> IP|TID|TIME|CALLCHAIN|CPU|PERIOD, disabled: 1, inherit: 1, mmap: 1, comm: 1,
> freq: 1, task: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2:
> 1, comm_exec: 1
>
> Add a helper to determine if a session has a specific event name,
> and then use that helper for timehist. For perf sched timehist the
> analysis requires at least sched_switch event, so check for it.
That is a much better error message, thanks! I went on to take a look if
we had some pre-existing facility for that and found it, i.e. 'perf
kmem' already checks this and we get:
[root@jouet ~]# perf record usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.020 MB perf.data (7 samples) ]
[root@jouet ~]# perf kmem stat --page
No page allocation events found. Have you run 'perf kmem record --page'?
[root@jouet ~]# perf kmem stat --alloc
No slab allocation events found. Have you run 'perf kmem record --slab'?
[root@jouet ~]#
It uses things like:
if (kmem_page) {
struct perf_evsel *evsel;
evsel = perf_evlist__find_tracepoint_by_name(session->evlist,
"kmem:mm_page_alloc");
if (evsel == NULL) {
pr_err(errmsg, "page", "page");
goto out_delete;
}
- Arnaldo
> Now when analyzing a file without sched tracepoints you get:
> root@f21-vbox:/tmp$ perf sched timehist
> sched_switch event does not exist in file; nothing to analyze
>
> Signed-off-by: David Ahern <[email protected]>
> ---
> tools/perf/builtin-sched.c | 5 ++++-
> tools/perf/util/session.c | 12 ++++++++++++
> tools/perf/util/session.h | 2 ++
> 3 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index 870d94cd20ba..7c3c8176f51f 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -2629,8 +2629,11 @@ static int perf_sched__timehist(struct perf_sched
> *sched)
> if (perf_session__set_tracepoints_handlers(session, handlers))
> goto out;
>
> - if (!perf_session__has_traces(session, "record -R"))
> + /* sched_switch event at a minimum needs to exist */
> + if (!perf_session__has_event(session, "sched:sched_switch")) {
> + pr_err("sched_switch event does not exist in file; nothing to
> analyze\n");
> goto out;
> + }
>
> if (sched->show_migrations &&
> perf_session__set_tracepoints_handlers(session, migrate_handlers))
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index f268201048a0..9bb3e03dcd8e 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -1897,6 +1897,18 @@ bool perf_session__has_traces(struct perf_session
> *session, const char *msg)
> return false;
> }
>
> +bool perf_session__has_event(struct perf_session *session, const char *name)
> +{
> + struct perf_evsel *evsel;
> +
> + evlist__for_each_entry(session->evlist, evsel) {
> + if (!strcmp(perf_evsel__name(evsel), name))
> + return true;
> + }
> +
> + return false;
> +}
> +
> int maps__set_kallsyms_ref_reloc_sym(struct map **maps,
> const char *symbol_name, u64 addr)
> {
> diff --git a/tools/perf/util/session.h b/tools/perf/util/session.h
> index 4bd758553450..8609eca38c7f 100644
> --- a/tools/perf/util/session.h
> +++ b/tools/perf/util/session.h
> @@ -64,6 +64,8 @@ int perf_session__resolve_callchain(struct perf_session
> *session,
>
> bool perf_session__has_traces(struct perf_session *session, const char *msg);
>
> +bool perf_session__has_event(struct perf_session *session, const char *name);
> +
> void perf_event__attr_swap(struct perf_event_attr *attr);
>
> int perf_session__create_kernel_maps(struct perf_session *session);
> --
> 2.7.4 (Apple Git-66)
