This adds a simple perl script for reading two files as produced by the stackusage script and computing the changes in stack usage. For example: $ scripts/stackusage -o /tmp/old.su CC=gcc-4.7 -j8 fs/ext4/ $ scripts/stackusage -o /tmp/new.su CC=gcc-5.0 -j8 fs/ext4/ $ scripts/stackdelta /tmp/{old,new}.su | sort -k5,5g shows that gcc 5.0 generally produces less stack-hungry code than gcc 4.7. Obviously, the script can also be used for measuring the effect of commits, .config tweaks or whatnot.
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| 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 | } | ||