Added perfbd.py and block device performance sampling in bench-runner

Based loosely on Linux's perf tool, perfbd.py uses trace output with
backtraces to aggregate and show the block device usage of all functions
in a program, propagating block devices operation cost up the backtrace
for each operation.

This combined with --trace-period and --trace-freq for
sampling/filtering trace events allow the bench-runner to very
efficiently record the general cost of block device operations with very
little overhead.

Adopted this as the default side-effect of make bench, replacing
cycle-based performance measurements which are less important for
littlefs.

scripts/data.py

@@ -15,7 +15,6 @@
 import collections as co
 import csv
 import difflib
-import glob
 import itertools as it
 import math as m
 import os
@@ -24,7 +23,6 @@ import shlex
 import subprocess as sp
 
 
-OBJ_PATHS = ['*.o']
 NM_TOOL = ['nm']
 NM_TYPES = 'dDbB'
 OBJDUMP_TOOL = ['objdump']
@@ -126,16 +124,16 @@ class DataResult(co.namedtuple('DataResult', [
             self.size + other.size)
 
 
-def openio(path, mode='r'):
+def openio(path, mode='r', buffering=-1):
     if path == '-':
         if mode == 'r':
-            return os.fdopen(os.dup(sys.stdin.fileno()), 'r')
+            return os.fdopen(os.dup(sys.stdin.fileno()), mode, buffering)
         else:
-            return os.fdopen(os.dup(sys.stdout.fileno()), 'w')
+            return os.fdopen(os.dup(sys.stdout.fileno()), mode, buffering)
     else:
-        return open(path, mode)
+        return open(path, mode, buffering)
 
-def collect(paths, *,
+def collect(obj_paths, *,
         nm_tool=NM_TOOL,
         nm_types=NM_TYPES,
         objdump_tool=OBJDUMP_TOOL,
@@ -147,17 +145,17 @@ def collect(paths, *,
         ' (?P<type>[%s])' % re.escape(nm_types) +
         ' (?P<func>.+?)$')
     line_pattern = re.compile(
-        '^\s+(?P<no>[0-9]+)\s+'
-            '(?:(?P<dir>[0-9]+)\s+)?'
-            '.*\s+'
-            '(?P<path>[^\s]+)$')
+        '^\s+(?P<no>[0-9]+)'
+            '(?:\s+(?P<dir>[0-9]+))?'
+            '\s+.*'
+            '\s+(?P<path>[^\s]+)$')
     info_pattern = re.compile(
         '^(?:.*(?P<tag>DW_TAG_[a-z_]+).*'
-            '|^.*DW_AT_name.*:\s*(?P<name>[^:\s]+)\s*'
-            '|^.*DW_AT_decl_file.*:\s*(?P<file>[0-9]+)\s*)$')
+            '|.*DW_AT_name.*:\s*(?P<name>[^:\s]+)\s*'
+            '|.*DW_AT_decl_file.*:\s*(?P<file>[0-9]+)\s*)$')
 
     results = []
-    for path in paths:
+    for path in obj_paths:
         # guess the source, if we have debug-info we'll replace this later
         file = re.sub('(\.o)?$', '.c', path, 1)
 
@@ -520,20 +518,7 @@ def main(obj_paths, *,
         **args):
     # find sizes
     if not args.get('use', None):
-        # find .o files
-        paths = []
-        for path in obj_paths:
-            if os.path.isdir(path):
-                path = path + '/*.o'
-
-            for path in glob.glob(path):
-                paths.append(path)
-
-        if not paths:
-            print("error: no .o files found in %r?" % obj_paths)
-            sys.exit(-1)
-
-        results = collect(paths, **args)
+        results = collect(obj_paths, **args)
     else:
         results = []
         with openio(args['use']) as f:
@@ -613,9 +598,7 @@ if __name__ == "__main__":
     parser.add_argument(
         'obj_paths',
         nargs='*',
-        default=OBJ_PATHS,
-        help="Description of where to find *.o files. May be a directory "
-            "or a list of paths. Defaults to %r." % OBJ_PATHS)
+        help="Input *.o files.")
     parser.add_argument(
         '-v', '--verbose',
         action='store_true',