perf trace: Make --(min,max}-stack imply "--call-graph dwarf"

If one uses:

  # perf trace --min-stack 16

Then it implicitly means that callgraphs should be enabled, and the best
option in terms of widespread availability is "dwarf".

Further work needed to choose a better alternative, LBR, in capable
systems.

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-xtjmnpkyk42npekxz3kynzmx@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/Documentation/perf-trace.txt b/tools/perf/Documentation/perf-trace.txt
index 4e8baa7..146c6db 100644 (file)
--- a/tools/perf/Documentation/perf-trace.txt
+++ b/tools/perf/Documentation/perf-trace.txt
@@ -136,12 +136,18 @@ the thread executes on the designated CPUs. Default is to monitor all CPUs.
         not limiting, the overhead of callchains needs to be set via the
         knobs in --call-graph dwarf.
 
+        Implies '--call-graph dwarf' when --call-graph not present on the
+        command line, on systems where DWARF unwinding was built in.
+
         Default: 127
 
 --min-stack::
         Set the stack depth limit when parsing the callchain, anything
         below the specified depth will be ignored. Disabled by default.
 
+        Implies '--call-graph dwarf' when --call-graph not present on the
+        command line, on systems where DWARF unwinding was built in.
+
 --proc-map-timeout::
        When processing pre-existing threads /proc/XXX/mmap, it may take a long time,
        because the file may be huge. A time out is needed in such cases.

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 6a64cb1..19f5100 100644 (file)
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -3047,7 +3047,7 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
                .show_comm = true,
                .trace_syscalls = true,
                .kernel_syscallchains = false,
-               .max_stack = PERF_MAX_STACK_DEPTH,
+               .max_stack = UINT_MAX,
        };
        const char *output_name = NULL;
        const char *ev_qualifier_str = NULL;
@@ -3109,6 +3109,7 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
                        "per thread proc mmap processing timeout in ms"),
        OPT_END()
        };
+       bool max_stack_user_set = true;
        const char * const trace_subcommands[] = { "record", NULL };
        int err;
        char bf[BUFSIZ];
@@ -3142,6 +3143,16 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
                trace.opts.sample_time = true;
        }
 
+       if (trace.max_stack == UINT_MAX) {
+               trace.max_stack = PERF_MAX_STACK_DEPTH;
+               max_stack_user_set = false;
+       }
+
+#ifdef HAVE_DWARF_UNWIND_SUPPORT
+       if ((trace.min_stack || max_stack_user_set) && !trace.opts.callgraph_set)
+               record_opts__parse_callchain(&trace.opts, &callchain_param, "dwarf", false);
+#endif
+
        if (trace.opts.callgraph_set)
                symbol_conf.use_callchain = true;