perf report: Show call graph from reference events

Introduce --show-ref-call-graph for perf report to print reference
callgraph for no callgraph event.

Here is an example.

 perf report --show-ref-call-graph --stdio

 # To display the perf.data header info, please use
 --header/--header-only options.
 #
 #
 # Total Lost Samples: 0
 #
 # Samples: 5  of event 'cpu/cpu-cycles,call-graph=fp/'
 # Event count (approx.): 144985
 #
 # Children      Self  Command  Shared Object     Symbol
 # ........  ........  .......  ................  ........................................
 #
    72.30%     0.00%  sleep    [kernel.vmlinux]  [k] entry_SYSCALL_64_fastpath
              |
              ---entry_SYSCALL_64_fastpath
                 |
                 |--22.62%-- __GI___libc_nanosleep
                  --77.38%-- [...]

......

 # Samples: 6  of event 'cpu/instructions,call-graph=no/', show reference callgraph
 # Event count (approx.): 172780
 #
 # Children      Self  Command  Shared Object     Symbol
 # ........  ........  .......  ................  ........................................
 #
    73.16%     0.00%  sleep    [kernel.vmlinux]  [k] entry_SYSCALL_64_fastpath
              |
              ---entry_SYSCALL_64_fastpath
                 |
                 |--31.44%-- __GI___libc_nanosleep
                  --68.56%-- [...]

Signed-off-by: Kan Liang <kan.liang@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1439289050-40510-3-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

5 files changed, 33 insertions, 4 deletions

diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
index 7b07d19e2d54..a18ba757a0ed 100644
--- a/tools/perf/Documentation/perf-report.txt
+++ b/tools/perf/Documentation/perf-report.txt
@@ -359,6 +359,17 @@ OPTIONS
 --full-source-path::
         Show the full path for source files for srcline output.
 
+--show-ref-call-graph::
+        When multiple events are sampled, it may not be needed to collect
+        callgraphs for all of them. The sample sites are usually nearby,
+        and it's enough to collect the callgraphs on a reference event.
+        So user can use "call-graph=no" event modifier to disable callgraph
+        for other events to reduce the overhead.
+        However, perf report cannot show callgraphs for the event which
+        disable the callgraph.
+        This option extends the perf report to show reference callgraphs,
+        which collected by reference event, in no callgraph event.
+
 include::callchain-overhead-calculation.txt[]
 
 SEE ALSO
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index f301e865001f..62b285e32aa5 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -316,6 +316,11 @@ static size_t hists__fprintf_nr_sample_events(struct hists *hists, struct report
         if (evname != NULL)
                 ret += fprintf(fp, " of event '%s'", evname);
 
+        if (symbol_conf.show_ref_callgraph &&
+            strstr(evname, "call-graph=no")) {
+                ret += fprintf(fp, ", show reference callgraph");
+        }
+
         if (rep->mem_mode) {
                 ret += fprintf(fp, "\n# Total weight : %" PRIu64, nr_events);
                 ret += fprintf(fp, "\n# Sort order   : %s", sort_order ? : default_mem_sort_order);
@@ -740,6 +745,8 @@ int cmd_report(int argc, const char **argv, const char *prefix __maybe_unused)
                             itrace_parse_synth_opts),
         OPT_BOOLEAN(0, "full-source-path", &srcline_full_filename,
                         "Show full source file name path for source lines"),
+        OPT_BOOLEAN(0, "show-ref-call-graph", &symbol_conf.show_ref_callgraph,
+                    "Show callgraph from reference event"),
         OPT_END()
         };
         struct perf_data_file file = {
diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
index f296b7348449..10c7ec041039 100644
--- a/tools/perf/ui/browsers/hists.c
+++ b/tools/perf/ui/browsers/hists.c
@@ -1267,6 +1267,8 @@ static int hists__browser_title(struct hists *hists,
         const char *ev_name = perf_evsel__name(evsel);
         char buf[512];
         size_t buflen = sizeof(buf);
+        char ref[30] = " show reference callgraph, ";
+        bool enable_ref = false;
 
         if (symbol_conf.filter_relative) {
                 nr_samples = hists->stats.nr_non_filtered_samples;
@@ -1292,10 +1294,13 @@ static int hists__browser_title(struct hists *hists,
                 }
         }
 
+        if (symbol_conf.show_ref_callgraph &&
+            strstr(ev_name, "call-graph=no"))
+                enable_ref = true;
         nr_samples = convert_unit(nr_samples, &unit);
         printed = scnprintf(bf, size,
-                           "Samples: %lu%c of event '%s', Event count (approx.): %" PRIu64,
-                           nr_samples, unit, ev_name, nr_events);
+                           "Samples: %lu%c of event '%s',%sEvent count (approx.): %" PRIu64,
+                           nr_samples, unit, ev_name, enable_ref ? ref : " ", nr_events);
 
 
         if (hists->uid_filter_str)
diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 1cd785b5b56e..08b6cd945f1e 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -1141,7 +1141,12 @@ void hists__output_resort(struct hists *hists, struct ui_progress *prog)
         struct hist_entry *n;
         u64 min_callchain_hits;
         struct perf_evsel *evsel = hists_to_evsel(hists);
-        bool use_callchain = evsel ? (evsel->attr.sample_type & PERF_SAMPLE_CALLCHAIN) : symbol_conf.use_callchain;
+        bool use_callchain;
+
+        if (evsel && !symbol_conf.show_ref_callgraph)
+                use_callchain = evsel->attr.sample_type & PERF_SAMPLE_CALLCHAIN;
+        else
+                use_callchain = symbol_conf.use_callchain;
 
         min_callchain_hits = hists->stats.total_period * (callchain_param.min_percent / 100);
 
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index b98ce51af142..a4cde92afbad 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -106,7 +106,8 @@ struct symbol_conf {
                         filter_relative,
                         show_hist_headers,
                         branch_callstack,
-                        has_filter;
+                        has_filter,
+                        show_ref_callgraph;
         const char      *vmlinux_name,
                         *kallsyms_name,
                         *source_prefix,