scripts/bloat-o-meter: don't use readlines()

readlines() conses whole list before doing anything which is slower for
big object files.  Use per line iterator.

Speed up is ~2% on "allyesconfig" type of kernel.

    $ perf stat -r 16 taskset -c 15 ./scripts/bloat-o-meter ../vmlinux-000 ../obj/vmlinux >/dev/null
	...

  Before:  7.247708646 seconds time elapsed                ( +-  0.28% )
  After:   7.091202853 seconds time elapsed                ( +-  0.15% )

Link: http://lkml.kernel.org/r/20161119004143.GA1200@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/bloat-o-meter

@@ -18,17 +18,18 @@ if len(sys.argv) != 3:
 
 def getsizes(file):
     sym = {}
-    for l in os.popen("nm --size-sort " + file).readlines():
-        size, type, name = l[:-1].split()
-        if type in "tTdDbBrR":
-            # strip generated symbols
-            if name.startswith("__mod_"): continue
-            if name.startswith("SyS_"): continue
-            if name.startswith("compat_SyS_"): continue
-            if name == "linux_banner": continue
-            # statics and some other optimizations adds random .NUMBER
-            name = re.sub(r'\.[0-9]+', '', name)
-            sym[name] = sym.get(name, 0) + int(size, 16)
+    with os.popen("nm --size-sort " + file) as f:
+        for line in f:
+            size, type, name = line.split()
+            if type in "tTdDbBrR":
+                # strip generated symbols
+                if name.startswith("__mod_"): continue
+                if name.startswith("SyS_"): continue
+                if name.startswith("compat_SyS_"): continue
+                if name == "linux_banner": continue
+                # statics and some other optimizations adds random .NUMBER
+                name = re.sub(r'\.[0-9]+', '', name)
+                sym[name] = sym.get(name, 0) + int(size, 16)
     return sym
 
 old = getsizes(sys.argv[1])