diff --git a/scripts/reduce-config.pl b/scripts/reduce-config.pl
new file mode 100755
index 000000000..ebccab42e
--- /dev/null
+++ b/scripts/reduce-config.pl
@@ -0,0 +1,86 @@
+#! /usr/bin/perl
+use strict;
+use warnings;
+
+our $CONFIG_IN='./config.in';
+our $CONFIG_OUT='./config.reduced';
+
+my @lines;
+my @disa;
+
+sub read_config {
+	my ($fn)=@_;
+	open my $in,'<',$CONFIG_IN or die "$CONFIG_IN: $!\n";
+	@lines=(<$in>);
+}
+
+sub write_config {
+	my ($fn)=@_;
+	open my $out,'>',$fn or die "$fn: $!\n";
+	for (my $i=0;$i<@lines;$i++) {
+		print $out $lines[$i] unless $disa[$i];
+	}
+	close $out;
+}
+
+sub build {
+	write_config('.config');
+	system 'make olddefconfig>/dev/null';
+	if ($?) {
+		warn "make failed: $?\n";
+		return 0;
+	}
+	return 1;
+}
+
+sub try {
+	write_config('./config');
+	build() or return 0;
+	system 'cmp','-s','.config','.config.target.tmp';
+	if ($?==0) {
+		return 1;
+	} else {
+		return 0;
+	}
+}
+
+read_config($CONFIG_IN);
+build() or die "failed to build with original config\n";
+system 'cp','.config','.config.target.tmp' and exit 1;
+
+my $p=0;
+my $progress=0;
+
+while (1) {
+	if ($disa[$p]) {
+		;
+	} else {
+		$disa[$p]=1;
+		if (try) {
+			$progress=1;
+			warn "disable $lines[$p]";
+		} else {
+			$disa[$p]=0;
+			warn "keep    $lines[$p]";
+		}
+	}
+	$p++;
+	if ($p>=@lines) {
+		if ($progress) {
+			warn "starting over\n";
+			$p=0;
+			$progress=0;
+		}
+		else {
+			warn "no progress. finished\n";
+			last;
+		}
+	}
+}
+
+# generate a valid .config
+try() or die "final compare failed\n";
+
+# and save the result
+write_config($CONFIG_OUT);
+