tools: reduce test runner timing overhead

RunProcess sleeps after polling even when the child has already exited.
Skip that sleep, saving up to 100 ms per test.

Sort --time results in descending order to display the 20 slowest tests.

Signed-off-by: Filip Skokan <panva.ip@gmail.com>
Assisted-by: Codex
PR-URL: #65980
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: LiviaMedeiros <livia@cirno.name>

Author: panva

tools/test.py

@@ -741,10 +741,11 @@ def RunProcess(context, timeout, args, **rest):
       timed_out = True
     else:
       exit_code = process.poll()
-      time.sleep(sleep_time)
-      sleep_time = sleep_time * SLEEP_TIME_FACTOR
-      if sleep_time > MAX_SLEEP_TIME:
-        sleep_time = MAX_SLEEP_TIME
+      if exit_code is None:
+        time.sleep(sleep_time)
+        sleep_time = sleep_time * SLEEP_TIME_FACTOR
+        if sleep_time > MAX_SLEEP_TIME:
+          sleep_time = MAX_SLEEP_TIME
   return (process, exit_code, timed_out)
 
 
@@ -1846,7 +1847,7 @@ def should_keep(case):
     print()
     sys.stderr.write("--- Total time: %s ---\n" % FormatTime(duration))
     timed_tests = [ t for t in cases_to_run if not t.duration is None ]
-    timed_tests.sort(key=lambda x: x.duration)
+    timed_tests.sort(key=lambda x: x.duration, reverse=True)
     for i, entry in enumerate(timed_tests[:20], start=1):
       t = FormatTimedelta(entry.duration)
       sys.stderr.write("%4i (%s) %s\n" % (i, t, entry.GetLabel()))