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perf trace: Bump --mmap-pages when --call-graph is used by the root user

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To reduce the chances we'll overflow the mmap buffer, manual fine tuning
trumps this.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-wxygbxmp1v9mng1ea28wet02@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2016-04-15 17:52:34 -03:00
parent f5e7150cd9
commit f3e459d16a
2 changed files with 13 additions and 1 deletions
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4
tools/perf/Documentation/perf-trace.txt
View File

@ -123,6 +123,10 @@ the thread executes on the designated CPUs. Default is to monitor all CPUs.
man pages for details. The ones that are most useful in 'perf trace'
are 'dwarf' and 'lbr', where available, try: 'perf trace --call-graph dwarf'.
Using this will, for the root user, bump the value of --mmap-pages to 4
times the maximum for non-root users, based on the kernel.perf_event_mlock_kb
sysctl. This is done only if the user doesn't specify a --mmap-pages value.
--kernel-syscall-graph::
Show the kernel callchains on the syscall exit path.

10
tools/perf/builtin-trace.c
View File

@ -3110,6 +3110,7 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
OPT_END()
};
bool max_stack_user_set = true;
bool mmap_pages_user_set = true;
const char * const trace_subcommands[] = { "record", NULL };
int err;
char bf[BUFSIZ];
@ -3143,6 +3144,9 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
trace.opts.sample_time = true;
}
if (trace.opts.mmap_pages == UINT_MAX)
mmap_pages_user_set = false;
if (trace.max_stack == UINT_MAX) {
trace.max_stack = PERF_MAX_STACK_DEPTH;
max_stack_user_set = false;
@ -3153,8 +3157,12 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
record_opts__parse_callchain(&trace.opts, &callchain_param, "dwarf", false);
#endif
if (trace.opts.callgraph_set)
if (trace.opts.callgraph_set) {
if (!mmap_pages_user_set && geteuid() == 0)
trace.opts.mmap_pages = perf_event_mlock_kb_in_pages() * 4;
symbol_conf.use_callchain = true;
}
if (trace.evlist->nr_entries > 0)
evlist__set_evsel_handler(trace.evlist, trace__event_handler);