Re: [PATCH v1 3/5] perf evlist: Refactor evlist__scnprintf_evsels

Ian Rogers
2025-04-02T15:56:07Z

On Wed, Apr 2, 2025 at 8:26 AM Liang, Kan <kan.liang@linux.intel.com> wrote:
>
>
>
> On 2025-03-18 12:14 a.m., Ian Rogers wrote:
> > Switch output to using a strbuf so the storage can be resized. Rename
> > as scnprintf is no longer used.
> >
> > Signed-off-by: Ian Rogers <irogers@google.com>
> > ---
> > tools/perf/builtin-record.c | 9 ++++++---
> > tools/perf/util/evlist.c | 19 +++++++++----------
> > tools/perf/util/evlist.h | 3 ++-
> > 3 files changed, 17 insertions(+), 14 deletions(-)
> >
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index ba20bf7c011d..cea5959adadc 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -51,6 +51,7 @@
> > #include "util/clockid.h"
> > #include "util/off_cpu.h"
> > #include "util/bpf-filter.h"
> > +#include "util/strbuf.h"
> > #include "asm/bug.h"
> > #include "perf.h"
> > #include "cputopo.h"
> > @@ -2784,13 +2785,15 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> > record__auxtrace_snapshot_exit(rec);
> >
> > if (forks && workload_exec_errno) {
> > - char msg[STRERR_BUFSIZE], strevsels[2048];
> > + char msg[STRERR_BUFSIZE];
> > const char *emsg = str_error_r(workload_exec_errno, msg, sizeof(msg));
> > + struct strbuf sb = STRBUF_INIT;
> >
> > - evlist__scnprintf_evsels(rec->evlist, sizeof(strevsels), strevsels);
> > + evlist__format_evsels(rec->evlist, &sb);
> >
> > pr_err("Failed to collect '%s' for the '%s' workload: %s\n",
> > - strevsels, argv[0], emsg);
> > + sb.buf, argv[0], emsg);
> > + strbuf_release(&sb);
> > err = -1;
> > goto out_child;
> > }
> > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> > index 49e10d6981ad..96cfc7ed1512 100644
> > --- a/tools/perf/util/evlist.c
> > +++ b/tools/perf/util/evlist.c
> > @@ -35,6 +35,7 @@
> > #include "util/util.h"
> > #include "util/env.h"
> > #include "util/intel-tpebs.h"
> > +#include "util/strbuf.h"
> > #include <signal.h>
> > #include <unistd.h>
> > #include <sched.h>
> > @@ -2468,23 +2469,21 @@ struct evsel *evlist__find_evsel(struct evlist *evlist, int idx)
> > return NULL;
> > }
> >
> > -int evlist__scnprintf_evsels(struct evlist *evlist, size_t size, char *bf)
> > +void evlist__format_evsels(struct evlist *evlist, struct strbuf *sb)
> > {
> > struct evsel *evsel;
> > - int printed = 0;
> > + bool first = true;
> >
> > evlist__for_each_entry(evlist, evsel) {
> > if (evsel__is_dummy_event(evsel))
> > continue;
> > - if (size > (strlen(evsel__name(evsel)) + (printed ? 2 : 1))) {
> > - printed += scnprintf(bf + printed, size - printed, "%s%s", printed ? "," : "", evsel__name(evsel));
> > - } else {
> > - printed += scnprintf(bf + printed, size - printed, "%s...", printed ? "," : "");
> > - break;
> > - }
> > - }
> >
> > - return printed;
> > + if (!first)
> > + strbuf_addch(sb, ',');
> > +> + strbuf_addstr(sb, evsel__name(evsel));
>
> The evlist may include hundreds of events. The error msg will be too
> huge for the case.

I hear you, lots of uncore PMUs :-) I keep wanting to the PMU with an
evsel to be a list. As you suggest in the next feedback, let's add an
option to have some maximum for the perf record use case.

Thanks,
Ian

> Thanks,
> Kan
>
> > + first = false;
> > + }
> > }
> >
> > void evlist__check_mem_load_aux(struct evlist *evlist)
> > diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
> > index edcbf1c10e92..5fe5cfbbebb1 100644
> > --- a/tools/perf/util/evlist.h
> > +++ b/tools/perf/util/evlist.h
> > @@ -20,6 +20,7 @@ struct pollfd;
> > struct thread_map;
> > struct perf_cpu_map;
> > struct record_opts;
> > +struct strbuf;
> > struct target;
> >
> > /*
> > @@ -430,7 +431,7 @@ int event_enable_timer__process(struct event_enable_timer *eet);
> >
> > struct evsel *evlist__find_evsel(struct evlist *evlist, int idx);
> >
> > -int evlist__scnprintf_evsels(struct evlist *evlist, size_t size, char *bf);
> > +void evlist__format_evsels(struct evlist *evlist, struct strbuf *sb);
> > void evlist__check_mem_load_aux(struct evlist *evlist);
> > void evlist__warn_user_requested_cpus(struct evlist *evlist, const char *cpu_list);
> > void evlist__uniquify_name(struct evlist *evlist);
>