Commit 0c1d46a8 authored by Wang Nan's avatar Wang Nan Committed by Arnaldo Carvalho de Melo
Browse files

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: default avatarWang 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: default avatarHe Kuang <hekuang@huawei.com>
[ Updated man page ]
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent eca857ab

tools/perf/Documentation/perf-record.txt

+1 −1
Original line number Diff line number Diff line
@@ -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

--------

tools/perf/builtin-record.c

+29 −1
Original line number Diff line number Diff line
@@ -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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