perf record: Cache build-ID of hit DSOs only

It post-processes samples to find which DSO has samples.  Based on that
info, it can save used DSOs in the build-ID cache directory.  But for
some reason, it saves all DSOs without checking the hit mark.  Skipping
unused DSOs can give some speedup especially with --buildid-mmap being
default.

On my idle machine, `time perf record -a sleep 1` goes down from 3 sec
to 1.5 sec with this change.

Fixes: e29386c ("perf record: Add --buildid-mmap option to enable PERF_RECORD_MMAP2's build id")
Reviewed-by: Arnaldo Carvalho de Melo <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Namhyung Kim <[email protected]>

Author: namhyung

tools/perf/util/build-id.c

@@ -872,7 +872,7 @@ static int dso__cache_build_id(struct dso *dso, struct machine *machine,
 	char *allocated_name = NULL;
 	int ret = 0;
 
-	if (!dso__has_build_id(dso))
+	if (!dso__has_build_id(dso) || !dso__hit(dso))
 		return 0;
 
 	if (dso__is_kcore(dso)) {