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perf debug: Avoid calling eprintf() in pr_debugN() when verbose < n

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pr_debugN() unconditionally evaluated its arguments and called eprintf()
-> veprintf() before checking if verbose >= n. In hot paths such as
dso__load_sym_internal(), two pr_debug4() calls per symbol accounted for
~15% of total CPU time in 'perf top' even at the default verbose == 0.

Guard eprintf() in pr_debugN() with unlikely(verbose >= (n)) and define
pr_debug() in terms of pr_debugN(1, ...).

In test__parsing_callback() (tools/perf/tests/pmu-events.c), move the
test_generic_metric(mexp, 0) call out of the pr_debug() argument list so
the metric evaluation continues to run during 'perf test' when verbose
== 0.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alessio Podda <aleph.pi.gh@gmail.com>
Cc: Alireza Haghdoost <haghdoost@uber.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michael Liang <mliang@purestorage.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shimin Guo <shimin.guo@skydio.com>
Cc: Tanushree Shah <tshah@linux.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Ian Rogers 2026-10-25 23:50:44 -07:00 committed by Arnaldo Carvalho de Melo
parent 62d7cdc8d5
commit 2fb45894e8
2 changed files with 6 additions and 4 deletions
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5
tools/perf/tests/pmu-events.c
View File

@ -906,9 +906,12 @@ static int test__parsing_callback(const struct pmu_metric *pm,
struct metric_expr *mexp;
list_for_each_entry (mexp, &me->head, nd) {
double result;
if (strcmp(mexp->metric_name, pm->metric_name))
continue;
pr_debug("Result %f\n", test_generic_metric(mexp, 0));
result = test_generic_metric(mexp, 0);
pr_debug("Result %f\n", result);
err = 0;
(*failures)--;
goto out_err;

5
tools/perf/util/debug.h
View File

@ -33,10 +33,9 @@ extern int debug_type_profile;
})
#define pr_info(fmt, ...) \
eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_debug(fmt, ...) \
eprintf(1, verbose, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_debugN(n, fmt, ...) \
eprintf(n, verbose, pr_fmt(fmt), ##__VA_ARGS__)
(unlikely(verbose >= (n)) ? eprintf(n, verbose, pr_fmt(fmt), ##__VA_ARGS__) : 0)
#define pr_debug(fmt, ...) pr_debugN(1, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_debug2(fmt, ...) pr_debugN(2, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_debug3(fmt, ...) pr_debugN(3, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_debug4(fmt, ...) pr_debugN(4, pr_fmt(fmt), ##__VA_ARGS__)