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

Liang, Kan
2025-04-02T15:26:05Z

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);