From 46baf956987dca495ed44b1050e64939fae5c8ab Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Fri, 29 Nov 2019 12:25:05 +0000
Subject: git: async batch interface

This is a transitionary interface which does NOT require an
event loop.  It can be plugged into in current synchronous code
without major surgery.

It allows HTTP/1.1 pipelining-like functionality by taking
advantage of predictable and well-specified POSIX pipe semantics
by stuffing multiple git cat-file requests into the --batch pipe

With xt/git_async_cmp.t and GIANT_GIT_DIR=git.git, the async
interface is 10-25% faster than the synchronous interface since
it can keep the "git cat-file" process busier.

This is expected to improve performance on systems with slower
storage (but multiple cores).
---
 xt/git_async_cmp.t | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 xt/git_async_cmp.t

(limited to 'xt')

diff --git a/xt/git_async_cmp.t b/xt/git_async_cmp.t
new file mode 100644
index 00000000..f8ffe3d9
--- /dev/null
+++ b/xt/git_async_cmp.t
@@ -0,0 +1,61 @@
+#!perl -w
+# Copyright (C) 2019 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+use strict;
+use Test::More;
+use Benchmark qw(:all);
+use Digest::SHA;
+use PublicInbox::TestCommon;
+my $git_dir = $ENV{GIANT_GIT_DIR};
+plan 'skip_all' => "GIANT_GIT_DIR not defined for $0" unless defined($git_dir);
+use_ok 'PublicInbox::Git';
+my $git = PublicInbox::Git->new($git_dir);
+my @cat = qw(cat-file --buffer --batch-check --batch-all-objects);
+if (require_git(2.19, 1)) {
+	push @cat, '--unordered';
+} else {
+	warn "git <2.19, cat-file lacks --unordered, locality suffers\n";
+}
+my @dig;
+my $nr = $ENV{NR} || 1;
+my $async = timeit($nr, sub {
+	my $dig = Digest::SHA->new(1);
+	my $cb = sub {
+		my ($bref) = @_;
+		$dig->add($$bref);
+	};
+	my $cat = $git->popen(@cat);
+	$git->cat_async_begin;
+
+	foreach (<$cat>) {
+		my ($oid, undef, undef) = split(/ /);
+		$git->cat_async($oid, $cb);
+	}
+	close $cat or die "cat: $?";
+	$git->cat_async_wait;
+	push @dig, ['async', $dig->hexdigest ];
+});
+
+my $sync = timeit($nr, sub {
+	my $dig = Digest::SHA->new(1);
+	my $cat = $git->popen(@cat);
+	foreach (<$cat>) {
+		my ($oid, undef, undef) = split(/ /);
+		my $bref = $git->cat_file($oid);
+		$dig->add($$bref);
+	}
+	close $cat or die "cat: $?";
+	push @dig, ['sync', $dig->hexdigest ];
+});
+
+ok(scalar(@dig) >= 2, 'got some digests');
+my $ref = shift @dig;
+my $exp = $ref->[1];
+isnt($exp, Digest::SHA->new(1)->hexdigest, 'not empty');
+foreach (@dig) {
+	is($_->[1], $exp, "digest matches $_->[0] <=> $ref->[0]");
+}
+diag "sync=".timestr($sync);
+diag "async=".timestr($async);
+done_testing;
+1;
-- 
cgit v1.2.3-24-ge0c7