linux-kernel - [PATCH] perf record: Make sure to update build-ID cache

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Message-ID: <20251104042632.1560922-1-namhyung@kernel.org>
Date: Mon,  3 Nov 2025 20:26:32 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>
Cc: Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	James Clark <james.clark@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org
Subject: [PATCH] perf record: Make sure to update build-ID cache

Recent change on enabling --buildid-mmap by default brought an issue
with build-id handling.  With build-ID in MMAP2 records, we don't need
to save the build-ID table in the header are of a perf data file.

But the actual file contents still need to be cached in the debug
directory for annotation etc.  Split the build-ID header processing and
caching and make sure perf record to save hit DSOs in the build-ID cache
by moving perf_session__cache_build_ids() to the end of the record__
finish_output().

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/builtin-record.c | 30 +++++++++++++++---------------
 tools/perf/util/header.c    |  1 -
 2 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index ffb94a8339b03ec2..fe10bb7f35cbea05 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1890,15 +1890,14 @@ record__finish_output(struct record *rec)
 	}
 
 	/* Buildid scanning disabled or build ID in kernel and synthesized map events. */
-	if (!rec->no_buildid) {
+	if (!rec->no_buildid || !rec->no_buildid_cache) {
 		process_buildids(rec);
 
 		if (rec->buildid_all)
 			perf_session__dsos_hit_all(rec->session);
 	}
 	perf_session__write_header(rec->session, rec->evlist, fd, true);
-
-	return;
+	perf_session__cache_build_ids(rec->session);
 }
 
 static int record__synthesize_workload(struct record *rec, bool tail)
@@ -3083,7 +3082,7 @@ static int perf_record_config(const char *var, const char *value, void *cb)
 		else if (!strcmp(value, "no-cache"))
 			rec->no_buildid_cache = true;
 		else if (!strcmp(value, "skip"))
-			rec->no_buildid = true;
+			rec->no_buildid = rec->no_buildid_cache = true;
 		else if (!strcmp(value, "mmap"))
 			rec->buildid_mmap = true;
 		else if (!strcmp(value, "no-mmap"))
@@ -4192,24 +4191,25 @@ int cmd_record(int argc, const char **argv)
 		record.opts.record_switch_events = true;
 	}
 
-	if (!rec->buildid_mmap) {
-		pr_debug("Disabling build id in synthesized mmap2 events.\n");
-		symbol_conf.no_buildid_mmap2 = true;
-	} else if (rec->buildid_mmap_set) {
-		/*
-		 * Explicitly passing --buildid-mmap disables buildid processing
-		 * and cache generation.
-		 */
-		rec->no_buildid = true;
-	}
 	if (rec->buildid_mmap && !perf_can_record_build_id()) {
 		pr_warning("Missing support for build id in kernel mmap events.\n"
 			   "Disable this warning with --no-buildid-mmap\n");
 		rec->buildid_mmap = false;
 	}
+
 	if (rec->buildid_mmap) {
 		/* Enable perf_event_attr::build_id bit. */
 		rec->opts.build_id = true;
+		/* Disable build-ID table in the header. */
+		rec->no_buildid = true;
+	} else {
+		pr_debug("Disabling build id in synthesized mmap2 events.\n");
+		symbol_conf.no_buildid_mmap2 = true;
+	}
+
+	if (rec->no_buildid_set && rec->no_buildid) {
+		/* -B implies -N for historic reasons. */
+		rec->no_buildid_cache = true;
 	}
 
 	if (rec->opts.record_cgroup && !perf_can_record_cgroup()) {
@@ -4306,7 +4306,7 @@ int cmd_record(int argc, const char **argv)
 
 	err = -ENOMEM;
 
-	if (rec->no_buildid_cache || rec->no_buildid) {
+	if (rec->no_buildid_cache) {
 		disable_buildid_cache();
 	} else if (rec->switch_output.enabled) {
 		/*
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 4f2a6e10ed5cc0bd..4de7ca16b5522c47 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -335,7 +335,6 @@ static int write_build_id(struct feat_fd *ff,
 		pr_debug("failed to write buildid table\n");
 		return err;
 	}
-	perf_session__cache_build_ids(session);
 
 	return 0;
 }
-- 
2.51.2.997.g839fc31de9-goog