scripts/stackdelta

   1 #!/usr/bin/perl
   2
   3 # Read two files produced by the stackusage script, and show the
   4 # delta between them.
   5 #
   6 # Currently, only shows changes for functions listed in both files. We
   7 # could add an option to show also functions which have vanished or
   8 # appeared (which would often be due to gcc making other inlining
   9 # decisions).
  10 #
  11 # Another possible option would be a minimum absolute value for the
  12 # delta.
  13 #
  14 # A third possibility is for sorting by delta, but that can be
  15 # achieved by piping to sort -k5,5g.
  16
  17 sub read_stack_usage_file {
  18     my %su;
  19     my $f = shift;
  20     open(my $fh, '<', $f)
  21         or die "cannot open $f: $!";
  22     while (<$fh>) {
  23         chomp;
  24         my ($file, $func, $size, $type) = split;
  25         # Old versions of gcc (at least 4.7) have an annoying quirk in
  26         # that a (static) function whose name has been changed into
  27         # for example ext4_find_unwritten_pgoff.isra.11 will show up
  28         # in the .su file with a name of just "11". Since such a
  29         # numeric suffix is likely to change across different
  30         # commits/compilers/.configs or whatever else we're trying to
  31         # tweak, we can't really track those functions, so we just
  32         # silently skip them.
  33         #
  34         # Newer gcc (at least 5.0) report the full name, so again,
  35         # since the suffix is likely to change, we strip it.
  36         next if $func =~ m/^[0-9]+$/;
  37         $func =~ s/\..*$//;
  38         # Line numbers are likely to change; strip those.
  39         $file =~ s/:[0-9]+$//;
  40         $su{"${file}\t${func}"} = {size => $size, type => $type};
  41     }
  42     close($fh);
  43     return \%su;
  44 }
  45
  46 @ARGV == 2
  47     or die "usage: $0 <old> <new>";
  48
  49 my $old = read_stack_usage_file($ARGV[0]);
  50 my $new = read_stack_usage_file($ARGV[1]);
  51 my @common = sort grep {exists $new->{$_}} keys %$old;
  52 for (@common) {
  53     my $x = $old->{$_}{size};
  54     my $y = $new->{$_}{size};
  55     my $delta = $y - $x;
  56     if ($delta) {
  57         printf "%s\t%d\t%d\t%+d\n", $_, $x, $y, $delta;
  58     }
  59 }