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git-svn: improve rebase/mkdirs performance
Processing empty_dir directives becomes extremely slow for svn repositories with a large enough history. This is due to using a single hash to store the list of empty directories, with the expensive step being purging items from that hash using grep+delete. Storing directories in a hash of hashes improves the performance of this purge step and removes a potentially lengthy delay after every rebase/mkdirs command. The svn repository with this behaviour has 110K commits with unhandled.log containing 170K empty_dir directives. This takes 10 minutes to process when using a single hash, vs 3 seconds with a hash of hashes. Signed-off-by: Dair Grant <dair@feralinteractive.com> Signed-off-by: Eric Wong <normalperson@yhbt.net>
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@ -1211,20 +1211,87 @@ sub do_fetch {
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sub mkemptydirs {
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my ($self, $r) = @_;
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# add/remove/collect a paths table
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#
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# Paths are split into a tree of nodes, stored as a hash of hashes.
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#
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# Each node contains a 'path' entry for the path (if any) associated
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# with that node and a 'children' entry for any nodes under that
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# location.
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#
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# Removing a path requires a hash lookup for each component then
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# dropping that node (and anything under it), which is substantially
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# faster than a grep slice into a single hash of paths for large
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# numbers of paths.
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#
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# For a large (200K) number of empty_dir directives this reduces
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# scanning time to 3 seconds vs 10 minutes for grep+delete on a single
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# hash of paths.
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sub add_path {
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my ($paths_table, $path) = @_;
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my $node_ref;
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foreach my $x (split('/', $path)) {
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if (!exists($paths_table->{$x})) {
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$paths_table->{$x} = { children => {} };
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}
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$node_ref = $paths_table->{$x};
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$paths_table = $paths_table->{$x}->{children};
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}
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$node_ref->{path} = $path;
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}
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sub remove_path {
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my ($paths_table, $path) = @_;
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my $nodes_ref;
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my $node_name;
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foreach my $x (split('/', $path)) {
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if (!exists($paths_table->{$x})) {
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return;
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}
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$nodes_ref = $paths_table;
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$node_name = $x;
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$paths_table = $paths_table->{$x}->{children};
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}
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delete($nodes_ref->{$node_name});
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}
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sub collect_paths {
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my ($paths_table, $paths_ref) = @_;
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foreach my $v (values %$paths_table) {
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my $p = $v->{path};
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my $c = $v->{children};
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collect_paths($c, $paths_ref);
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if (defined($p)) {
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push(@$paths_ref, $p);
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}
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}
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}
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sub scan {
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my ($r, $empty_dirs, $line) = @_;
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my ($r, $paths_table, $line) = @_;
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if (defined $r && $line =~ /^r(\d+)$/) {
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return 0 if $1 > $r;
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} elsif ($line =~ /^ \+empty_dir: (.+)$/) {
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$empty_dirs->{$1} = 1;
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add_path($paths_table, $1);
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} elsif ($line =~ /^ \-empty_dir: (.+)$/) {
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my @d = grep {m[^\Q$1\E(/|$)]} (keys %$empty_dirs);
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delete @$empty_dirs{@d};
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remove_path($paths_table, $1);
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}
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1; # continue
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};
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my %empty_dirs = ();
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my @empty_dirs;
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my %paths_table;
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my $gz_file = "$self->{dir}/unhandled.log.gz";
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if (-f $gz_file) {
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if (!can_compress()) {
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@ -1235,7 +1302,7 @@ sub mkemptydirs {
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die "Unable to open $gz_file: $!\n";
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my $line;
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while ($gz->gzreadline($line) > 0) {
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scan($r, \%empty_dirs, $line) or last;
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scan($r, \%paths_table, $line) or last;
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}
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$gz->gzclose;
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}
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@ -1244,13 +1311,14 @@ sub mkemptydirs {
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if (open my $fh, '<', "$self->{dir}/unhandled.log") {
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binmode $fh or croak "binmode: $!";
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while (<$fh>) {
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scan($r, \%empty_dirs, $_) or last;
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scan($r, \%paths_table, $_) or last;
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}
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close $fh;
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}
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collect_paths(\%paths_table, \@empty_dirs);
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my $strip = qr/\A\Q@{[$self->path]}\E(?:\/|$)/;
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foreach my $d (sort keys %empty_dirs) {
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foreach my $d (sort @empty_dirs) {
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$d = uri_decode($d);
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$d =~ s/$strip//;
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next unless length($d);
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