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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>
This commit is contained in:
Wang Nan 2016-04-20 18:59:52 +00:00 committed by Arnaldo Carvalho de Melo
parent eca857ab38
commit 0c1d46a879
2 changed files with 30 additions and 2 deletions
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2
tools/perf/Documentation/perf-record.txt
View File

@ -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 that gets then processed, possibly via a perf script, to decide if that
particular perf.data snapshot should be kept or not. particular perf.data snapshot should be kept or not.
Implies --timestamp-filename. Implies --timestamp-filename, --no-buildid and --no-buildid-cache.
SEE ALSO SEE ALSO
-------- --------

30
tools/perf/builtin-record.c
View File

@ -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" "If some relocation was applied (e.g. kexec) symbols may be misresolved\n"
"even with a suitable vmlinux or kallsyms file.\n\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(); 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 && if (rec->evlist->nr_entries == 0 &&
perf_evlist__add_default(rec->evlist) < 0) { perf_evlist__add_default(rec->evlist) < 0) {