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Subject[tip:perf/core] perf record: Disable buildid cache options by default in switch output mode
Commit-ID:  0c1d46a8796e8309f1ca693e5cad6f318e4b8159
Gitweb: http://git.kernel.org/tip/0c1d46a8796e8309f1ca693e5cad6f318e4b8159
Author: Wang Nan <wangnan0@huawei.com>
AuthorDate: Wed, 20 Apr 2016 18:59:52 +0000
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Thu, 28 Apr 2016 09:58:59 -0300

perf record: Disable buildid cache options by default in switch output mode

The cost of buildid cache processing is high: reading all events in
output perf.data, opening each elf file to read buildids then copying
them into ~/.debug directory. In switch output mode, these heavy works
block perf from receiving perf events for too long.

Enable no-buildid and no-buildid-cache by default if --switch-output is
provided. Still allow user use --no-no-buildid to explicitly enable
buildid in this case.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1461178794-40467-6-git-send-email-wangnan0@huawei.com
Signed-off-by: He Kuang <hekuang@huawei.com>
[ Updated man page ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/Documentation/perf-record.txt | 2 +-
tools/perf/builtin-record.c | 30 +++++++++++++++++++++++++++++-
2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 79a8a14..8dbee83 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -358,7 +358,7 @@ A possible use case is to, given an external event, slice the perf.data file
that gets then processed, possibly via a perf script, to decide if that
particular perf.data snapshot should be kept or not.

-Implies --timestamp-filename.
+Implies --timestamp-filename, --no-buildid and --no-buildid-cache.

SEE ALSO
--------
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 80b805b..178b49e 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1387,8 +1387,36 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
"If some relocation was applied (e.g. kexec) symbols may be misresolved\n"
"even with a suitable vmlinux or kallsyms file.\n\n");

- if (rec->no_buildid_cache || rec->no_buildid)
+ if (rec->no_buildid_cache || rec->no_buildid) {
disable_buildid_cache();
+ } else if (rec->switch_output) {
+ /*
+ * In 'perf record --switch-output', disable buildid
+ * generation by default to reduce data file switching
+ * overhead. Still generate buildid if they are required
+ * explicitly using
+ *
+ * perf record --signal-trigger --no-no-buildid \
+ * --no-no-buildid-cache
+ *
+ * Following code equals to:
+ *
+ * if ((rec->no_buildid || !rec->no_buildid_set) &&
+ * (rec->no_buildid_cache || !rec->no_buildid_cache_set))
+ * disable_buildid_cache();
+ */
+ bool disable = true;
+
+ if (rec->no_buildid_set && !rec->no_buildid)
+ disable = false;
+ if (rec->no_buildid_cache_set && !rec->no_buildid_cache)
+ disable = false;
+ if (disable) {
+ rec->no_buildid = true;
+ rec->no_buildid_cache = true;
+ disable_buildid_cache();
+ }
+ }

if (rec->evlist->nr_entries == 0 &&
perf_evlist__add_default(rec->evlist) < 0) {
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