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));
+		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);
-- 
2.49.0.rc1.451.g8f38331e32-goog

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.

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);

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);
>