tests: disable fsync everywhere

Eric Wong · gitster · commit 412e4caee387 · 2021-10-29T10:22:40.000-07:00
The "GIT_TEST_FSYNC" environment variable now exists for
disabling fsync() even on packfiles and other "critical" data.

Running "make test -j8 NO_SVN_TESTS=1" on a noisy 8-core system
on an HDD, test runtime drops from ~4 minutes down to ~3 minutes.
Using "GIT_TEST_FSYNC=1" re-enables fsync() for comparison
purposes.

SVN interopability tests are minimally affected since SVN will
still use fsync in various places.

This will also be useful for 3rd-party tools which create
throwaway git repositories of temporary data, but remains
undocumented for end users.

Signed-off-by: Eric Wong &lt;e@80x24.org&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/cache.h b/cache.h
@@ -985,6 +985,7 @@ extern int read_replace_refs;
 extern char *git_replace_ref_base;
 
 extern int fsync_object_files;
+extern int use_fsync;
 extern int core_preload_index;
 extern int precomposed_unicode;
 extern int protect_hfs;
diff --git a/environment.c b/environment.c
@@ -43,6 +43,7 @@ const char *git_hooks_path;
 int zlib_compression_level = Z_BEST_SPEED;
 int pack_compression_level = Z_DEFAULT_COMPRESSION;
 int fsync_object_files;
+int use_fsync = -1;
 size_t packed_git_window_size = DEFAULT_PACKED_GIT_WINDOW_SIZE;
 size_t packed_git_limit = DEFAULT_PACKED_GIT_LIMIT;
 size_t delta_base_cache_limit = 96 * 1024 * 1024;
diff --git a/git-cvsserver.perl b/git-cvsserver.perl
@@ -3607,6 +3607,22 @@ package GITCVS::updater;
 use strict;
 use warnings;
 use DBI;
+our $_use_fsync;
+
+# n.b. consider using Git.pm
+sub use_fsync {
+    if (!defined($_use_fsync)) {
+        my $x = $ENV{GIT_TEST_FSYNC};
+        if (defined $x) {
+            local $ENV{GIT_CONFIG};
+            delete $ENV{GIT_CONFIG};
+            my $v = ::safe_pipe_capture('git', '-c', "test.fsync=$x",
+                                        qw(config --type=bool test.fsync));
+            $_use_fsync = defined($v) ? ($v eq "true\n") : 1;
+        }
+    }
+    $_use_fsync;
+}
 
 =head1 METHODS
 
@@ -3676,6 +3692,9 @@ sub new
                                 $self->{dbuser},
                                 $self->{dbpass});
     die "Error connecting to database\n" unless defined $self->{dbh};
+    if ($self->{dbdriver} eq 'SQLite' && !use_fsync()) {
+        $self->{dbh}->do('PRAGMA synchronous = OFF');
+    }
 
     $self->{tables} = {};
     foreach my $table ( keys %{$self->{dbh}->table_info(undef,undef,undef,'TABLE')->fetchall_hashref('TABLE_NAME')} )
diff --git a/perl/Git/SVN.pm b/perl/Git/SVN.pm
@@ -6,7 +6,7 @@ use constant rev_map_fmt => 'NH*';
 use vars qw/$_no_metadata
             $_repack $_repack_flags $_use_svm_props $_head
             $_use_svnsync_props $no_reuse_existing
-	    $_use_log_author $_add_author_from $_localtime/;
+	    $_use_log_author $_add_author_from $_localtime $_use_fsync/;
 use Carp qw/croak/;
 use File::Path qw/mkpath/;
 use IPC::Open3;
@@ -2269,6 +2269,19 @@ sub mkfile {
 	}
 }
 
+# TODO: move this to Git.pm?
+sub use_fsync {
+	if (!defined($_use_fsync)) {
+		my $x = $ENV{GIT_TEST_FSYNC};
+		if (defined $x) {
+			my $v = command_oneline('-c', "test.fsync=$x",
+					qw(config --type=bool test.fsync));
+			$_use_fsync = defined($v) ? ($v eq "true\n") : 1;
+		}
+	}
+	$_use_fsync;
+}
+
 sub rev_map_set {
 	my ($self, $rev, $commit, $update_ref, $uuid) = @_;
 	defined $commit or die "missing arg3\n";
@@ -2290,7 +2303,7 @@ sub rev_map_set {
 	my $sync;
 	# both of these options make our .rev_db file very, very important
 	# and we can't afford to lose it because rebuild() won't work
-	if ($self->use_svm_props || $self->no_metadata) {
+	if (($self->use_svm_props || $self->no_metadata) && use_fsync()) {
 		require File::Copy;
 		$sync = 1;
 		File::Copy::copy($db, $db_lock) or die "rev_map_set(@_): ",
diff --git a/t/test-lib.sh b/t/test-lib.sh
@@ -489,6 +489,13 @@ then
 	export GIT_PERL_FATAL_WARNINGS
 fi
 
+case $GIT_TEST_FSYNC in
+'')
+	GIT_TEST_FSYNC=0
+	export GIT_TEST_FSYNC
+	;;
+esac
+
 # Add libc MALLOC and MALLOC_PERTURB test
 # only if we are not executing the test with valgrind
 if test -n "$valgrind" ||
diff --git a/write-or-die.c b/write-or-die.c
@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "config.h"
 #include "run-command.h"
 
 /*
@@ -57,6 +58,10 @@ void fprintf_or_die(FILE *f, const char *fmt, ...)
 
 void fsync_or_die(int fd, const char *msg)
 {
+	if (use_fsync < 0)
+		use_fsync = git_env_bool("GIT_TEST_FSYNC", 1);
+	if (!use_fsync)
+		return;
 	while (fsync(fd) < 0) {
 		if (errno != EINTR)
 			die_errno("fsync error on '%s'", msg);
