4 files changed, 25 insertions, 5 deletions

diff --git a/tools/perf/Documentation/perf-buildid-cache.txt b/tools/perf/Documentation/perf-buildid-cache.txt
index 0294c57b1f5e..cec6b57e8be6 100644
--- a/tools/perf/Documentation/perf-buildid-cache.txt
+++ b/tools/perf/Documentation/perf-buildid-cache.txt
@@ -41,9 +41,14 @@ OPTIONS
 --missing=::
         List missing build ids in the cache for the specified file.
 -u::
---update::
-        Update specified file of the cache. It can be used to update kallsyms
-        kernel dso to vmlinux in order to support annotation.
+--update=::
+        Update specified file of the cache. Note that this doesn't remove
+        older entires since those may be still needed for annotating old
+        (or remote) perf.data. Only if there is already a cache which has
+        exactly same build-id, that is replaced by new one. It can be used
+        to update kallsyms and kernel dso to vmlinux in order to support
+        annotation.
+
 -v::
 --verbose::
         Be more verbose.
diff --git a/tools/perf/builtin-buildid-cache.c b/tools/perf/builtin-buildid-cache.c
index d929d9544664..e7568f5844ad 100644
--- a/tools/perf/builtin-buildid-cache.c
+++ b/tools/perf/builtin-buildid-cache.c
@@ -255,7 +255,7 @@ static int build_id_cache__update_file(const char *filename)
         u8 build_id[BUILD_ID_SIZE];
         char sbuild_id[BUILD_ID_SIZE * 2 + 1];
 
-        int err;
+        int err = 0;
 
         if (filename__read_build_id(filename, &build_id, sizeof(build_id)) < 0) {
                 pr_debug("Couldn't read a build-id in %s\n", filename);
@@ -263,7 +263,9 @@ static int build_id_cache__update_file(const char *filename)
         }
 
         build_id__sprintf(build_id, sizeof(build_id), sbuild_id);
-        err = build_id_cache__remove_s(sbuild_id);
+        if (build_id_cache__cached(sbuild_id))
+                err = build_id_cache__remove_s(sbuild_id);
+
         if (!err)
                 err = build_id_cache__add_s(sbuild_id, filename, false, false);
 
diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index adbc36028636..0bc33be5a78c 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -352,6 +352,18 @@ static int build_id_cache__add_b(const u8 *build_id, size_t build_id_size,
         return build_id_cache__add_s(sbuild_id, name, is_kallsyms, is_vdso);
 }
 
+bool build_id_cache__cached(const char *sbuild_id)
+{
+        bool ret = false;
+        char *filename = build_id__filename(sbuild_id, NULL, 0);
+
+        if (filename && !access(filename, F_OK))
+                ret = true;
+        free(filename);
+
+        return ret;
+}
+
 int build_id_cache__remove_s(const char *sbuild_id)
 {
         const size_t size = PATH_MAX;
diff --git a/tools/perf/util/build-id.h b/tools/perf/util/build-id.h
index 31b3c6332a1a..2a094982f954 100644
--- a/tools/perf/util/build-id.h
+++ b/tools/perf/util/build-id.h
@@ -22,6 +22,7 @@ bool perf_session__read_build_ids(struct perf_session *session, bool with_hits);
 int perf_session__write_buildid_table(struct perf_session *session, int fd);
 int perf_session__cache_build_ids(struct perf_session *session);
 
+bool build_id_cache__cached(const char *sbuild_id);
 int build_id_cache__add_s(const char *sbuild_id,
                           const char *name, bool is_kallsyms, bool is_vdso);
 int build_id_cache__remove_s(const char *sbuild_id);