git: various minor speedups

While testing performance improvements elsewhere, I noticed some
micro-optimizations could give a small ~2-3% speedup in my test
using the git async API to parse a large inbox.

The `read' perlfunc already has read-in-full behavior (unless
git is killed unexpectedly), so there's no point in using a
loop.  SearchIdxShard in the parallel v2 indexing code path
never looped on `read', either.

Furthermore, we can avoid method dispatch overhead on ->getline
and ->print by using `readline' and `print' as ops which can be
resolved during the Perl compilation phase.

Finally, avoid passing the IO handle around as a parameter,
since avoiding hash lookups with a local variable has its own
costs in stack and refcount bumping.

Best off all, there's less code :>

diff --git a/lib/PublicInbox/Git.pm b/lib/PublicInbox/Git.pm
index 8410b2fce941d9d8b1e7f5b09557e97059a36146..057135efd0dccbf7ac69f7059f46518e72e951d3 100644 (file)
--- a/lib/PublicInbox/Git.pm
+++ b/lib/PublicInbox/Git.pm
@@ -125,59 +125,48 @@ sub _bidi_pipe {
        $self->{$in} = $in_r;
 }
 
-sub read_cat_in_full ($$$) {
-       my ($self, $in, $left) = @_;
-       my $offset = 0;
-       my $buf = '';
-       while ($left > 0) {
-               my $r = read($in, $buf, $left, $offset);
-               defined($r) or fail($self, "read failed: $!");
-               $r == 0 and fail($self, 'exited unexpectedly');
-               $left -= $r;
-               $offset += $r;
-       }
-       my $r = read($in, my $lf, 1);
-       defined($r) or fail($self, "read failed: $!");
-       fail($self, 'newline missing after blob') if ($r != 1 || $lf ne "\n");
+sub read_cat_in_full ($$) {
+       my ($self, $len) = @_;
+       ++$len; # for final "\n" added by git
+       read($self->{in}, my $buf, $len) == $len or fail($self, 'short read');
+       chop($buf) eq "\n" or fail($self, 'newline missing after blob');
        \$buf;
 }
 
-sub _cat_async_step ($$$) {
-       my ($self, $inflight, $in) = @_;
+sub _cat_async_step ($$) {
+       my ($self, $inflight) = @_;
        my $pair = shift @$inflight or die 'BUG: inflight empty';
        my ($cb, $arg) = @$pair;
        local $/ = "\n";
-       my $head = $in->getline;
+       my $head = readline($self->{in});
        $head =~ / missing$/ and return
                eval { $cb->(undef, undef, undef, undef, $arg) };
 
        $head =~ /^([0-9a-f]{40}) (\S+) ([0-9]+)$/ or
                fail($self, "Unexpected result from async git cat-file: $head");
        my ($oid_hex, $type, $size) = ($1, $2, $3 + 0);
-       my $bref = read_cat_in_full($self, $in, $size);
+       my $bref = read_cat_in_full($self, $size);
        eval { $cb->($bref, $oid_hex, $type, $size, $arg) };
 }
 
 sub cat_async_wait ($) {
        my ($self) = @_;
        my $inflight = delete $self->{inflight} or return;
-       my $in = $self->{in};
        while (scalar(@$inflight)) {
-               _cat_async_step($self, $inflight, $in);
+               _cat_async_step($self, $inflight);
        }
 }
 
 sub cat_file {
        my ($self, $obj, $ref) = @_;
-       my ($retried, $in, $head);
+       my ($retried, $head);
        cat_async_wait($self);
 again:
        batch_prepare($self);
-       $self->{out}->print($obj, "\n") or fail($self, "write error: $!");
+       print { $self->{out} } $obj, "\n" or fail($self, "write error: $!");
 
-       $in = $self->{in};
        local $/ = "\n";
-       $head = $in->getline;
+       $head = readline($self->{in});
        if ($head =~ / missing$/) {
                if (!$retried && alternates_changed($self)) {
                        $retried = 1;
@@ -191,7 +180,7 @@ again:
 
        my $size = $1;
        $$ref = $size if $ref;
-       read_cat_in_full($self, $in, $size);
+       read_cat_in_full($self, $size);
 }
 
 sub batch_prepare ($) { _bidi_pipe($_[0], qw(--batch in out pid)) }
@@ -199,9 +188,9 @@ sub batch_prepare ($) { _bidi_pipe($_[0], qw(--batch in out pid)) }
 sub check {
        my ($self, $obj) = @_;
        _bidi_pipe($self, qw(--batch-check in_c out_c pid_c err_c));
-       $self->{out_c}->print($obj, "\n") or fail($self, "write error: $!");
+       print { $self->{out_c} } $obj, "\n" or fail($self, "write error: $!");
        local $/ = "\n";
-       chomp(my $line = $self->{in_c}->getline);
+       chomp(my $line = readline($self->{in_c}));
        my ($hex, $type, $size) = split(' ', $line);
 
        # Future versions of git.git may show 'ambiguous', but for now,
@@ -320,10 +309,10 @@ sub cat_async ($$$;$) {
        my ($self, $oid, $cb, $arg) = @_;
        my $inflight = $self->{inflight} or die 'BUG: not in async';
        if (scalar(@$inflight) >= MAX_INFLIGHT) {
-               _cat_async_step($self, $inflight, $self->{in});
+               _cat_async_step($self, $inflight);
        }
 
-       $self->{out}->print($oid, "\n") or fail($self, "write error: $!");
+       print { $self->{out} } $oid, "\n" or fail($self, "write error: $!");
        push(@$inflight, [ $cb, $arg ]);
 }