perf evsel: Support printing callchains with arrows

The EVSEL__PRINT_CALLCHAIN_ARROW options can be used to print callchains
with arrows for readability.  It will be used 'sched timehist' command
like below:

    __schedule <- schedule <- schedule_timeout <- rcu_gp_kthread <- kthread <- ret_from_fork
    __schedule <- schedule <- schedule_timeout <- rcu_gp_kthread <- kthread <- ret_from_fork
    __schedule <- schedule <- worker_thread <- kthread <- ret_from_fork

Suggested-and-Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/20161116060634.28477-3-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 7 insertions, 0 deletions

diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 8cd7cd227483..27fa3a343577 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -391,6 +391,7 @@ int perf_evsel__fprintf(struct perf_evsel *evsel,
 #define EVSEL__PRINT_ONELINE            (1<<4)
 #define EVSEL__PRINT_SRCLINE            (1<<5)
 #define EVSEL__PRINT_UNKNOWN_AS_ADDR    (1<<6)
+#define EVSEL__PRINT_CALLCHAIN_ARROW    (1<<7)
 
 struct callchain_cursor;
 
diff --git a/tools/perf/util/evsel_fprintf.c b/tools/perf/util/evsel_fprintf.c
index ccb602397b60..53bb614feafb 100644
--- a/tools/perf/util/evsel_fprintf.c
+++ b/tools/perf/util/evsel_fprintf.c
@@ -108,7 +108,9 @@ int sample__fprintf_callchain(struct perf_sample *sample, int left_alignment,
         int print_oneline = print_opts & EVSEL__PRINT_ONELINE;
         int print_srcline = print_opts & EVSEL__PRINT_SRCLINE;
         int print_unknown_as_addr = print_opts & EVSEL__PRINT_UNKNOWN_AS_ADDR;
+        int print_arrow = print_opts & EVSEL__PRINT_CALLCHAIN_ARROW;
         char s = print_oneline ? ' ' : '\t';
+        bool first = true;
 
         if (sample->callchain) {
                 struct addr_location node_al;
@@ -124,6 +126,9 @@ int sample__fprintf_callchain(struct perf_sample *sample, int left_alignment,
 
                         printed += fprintf(fp, "%-*.*s", left_alignment, left_alignment, " ");
 
+                        if (print_arrow && !first)
+                                printed += fprintf(fp, " <-");
+
                         if (print_ip)
                                 printed += fprintf(fp, "%c%16" PRIx64, s, node->ip);
 
@@ -158,6 +163,7 @@ int sample__fprintf_callchain(struct perf_sample *sample, int left_alignment,
                                 printed += fprintf(fp, "\n");
 
                         callchain_cursor_advance(cursor);
+                        first = false;
                 }
         }