[PATCH v2 2/2] perf top: support hotkey to change sort order

[Jin Yao <yao.jin@linux.intel.com>]

It would be nice if we can use a hotkey in perf top browser to
select a event for sorting.

For example,
perf top --group -e cycles,instructions,cache-misses

Samples
                Overhead  Shared Object             Symbol
  40.03%  45.71%   0.03%  div                       [.] main
  20.46%  14.67%   0.21%  libc-2.27.so              [.] __random_r
  20.01%  19.54%   0.02%  libc-2.27.so              [.] __random
   9.68%  10.68%   0.00%  div                       [.] compute_flag
   4.32%   4.70%   0.00%  libc-2.27.so              [.] rand
   3.84%   3.43%   0.00%  div                       [.] rand@plt
   0.05%   0.05%   2.33%  libc-2.27.so              [.] __strcmp_sse2_unaligned
   0.04%   0.08%   2.43%  perf                      [.] perf_hpp__is_dynamic_en
   0.04%   0.02%   6.64%  perf                      [.] rb_next
   0.04%   0.01%   3.87%  perf                      [.] dso__find_symbol
   0.04%   0.04%   1.77%  perf                      [.] sort__dso_cmp

When user press hotkey '2' (event index, starting from 0), it indicates
to sort output by the third event in group (cache-misses).

Samples
                Overhead  Shared Object               Symbol
   4.07%   1.28%   6.68%  perf                        [.] rb_next
   3.57%   3.98%   4.11%  perf                        [.] __hists__insert_output
   3.67%  11.24%   3.60%  perf                        [.] perf_hpp__is_dynamic_e
   3.67%   3.20%   3.20%  perf                        [.] hpp__sort_overhead
   0.81%   0.06%   3.01%  perf                        [.] dso__find_symbol
   1.62%   5.47%   2.51%  perf                        [.] hists__match
   2.70%   1.86%   2.47%  libc-2.27.so                [.] _int_malloc
   0.19%   0.00%   2.29%  [kernel]                    [k] copy_page
   0.41%   0.32%   1.98%  perf                        [.] hists__decay_entries
   1.84%   3.67%   1.68%  perf                        [.] sort__dso_cmp
   0.16%   0.00%   1.63%  [kernel]                    [k] clear_page_erms

Now the output is sorted by cache-misses.

 v2:
 ---
 Zero the history if hotkey is pressed.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
---
 tools/perf/builtin-top.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 494c7b9a1022..29ddae7e1805 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -616,6 +616,7 @@ static void *display_thread_tui(void *arg)
 		.arg		= top,
 		.refresh	= top->delay_secs,
 	};
+	int ret;
 
 	/* In order to read symbols from other namespaces perf to  needs to call
 	 * setns(2).  This isn't permitted if the struct_fs has multiple users.
@@ -626,6 +627,7 @@ static void *display_thread_tui(void *arg)
 
 	prctl(PR_SET_NAME, "perf-top-UI", 0, 0, 0);
 
+repeat:
 	perf_top__sort_new_samples(top);
 
 	/*
@@ -638,13 +640,18 @@ static void *display_thread_tui(void *arg)
 		hists->uid_filter_str = top->record_opts.target.uid_str;
 	}
 
-	perf_evlist__tui_browse_hists(top->evlist, help, &hbt,
+	ret = perf_evlist__tui_browse_hists(top->evlist, help, &hbt,
 				      top->min_percent,
 				      &top->session->header.env,
 				      !top->record_opts.overwrite,
 				      &top->annotation_opts);
 
-	stop_top();
+	if (ret == K_RELOAD) {
+		top->zero = true;
+		goto repeat;
+	} else
+		stop_top();
+
 	return NULL;
 }
 
-- 
2.17.1