[PATCH] lock: reduce inotify wakeups

[Eric Wong <e@yhbt.net>]

We can reduce the amount of platform-specific code by always
relying on IN_MODIFY/NOTE_WRITE notifications from lock release.
This reduces the number of times our read-only daemons will
need to wake up when -watch sees no-op message changes
(e.g. replied, seen, recent flag changes).
---
 lib/PublicInbox/Import.pm     |  6 +++---
 lib/PublicInbox/InboxIdle.pm  |  8 ++++----
 lib/PublicInbox/KQNotify.pm   |  8 ++------
 lib/PublicInbox/Lock.pm       | 10 +++-------
 lib/PublicInbox/SearchIdx.pm  |  6 +++---
 lib/PublicInbox/V2Writable.pm |  3 ++-
 lib/PublicInbox/Xapcmd.pm     |  1 +
 7 files changed, 18 insertions(+), 24 deletions(-)

diff --git a/lib/PublicInbox/Import.pm b/lib/PublicInbox/Import.pm
index af35905b..ae508cd8 100644
--- a/lib/PublicInbox/Import.pm
+++ b/lib/PublicInbox/Import.pm
@@ -468,9 +468,9 @@ sub done {
 	waitpid($pid, 0) == $pid or die 'fast-import did not finish';
 	$? == 0 or die "fast-import failed: $?";
 
-	_update_git_info($self, 1) if delete $self->{nchg};
-
-	$self->lock_release;
+	my $nchg = delete $self->{nchg};
+	_update_git_info($self, 1) if $nchg;
+	$self->lock_release(!!$nchg);
 
 	$self->{git}->cleanup;
 }
diff --git a/lib/PublicInbox/InboxIdle.pm b/lib/PublicInbox/InboxIdle.pm
index d0bb43c5..97e9d532 100644
--- a/lib/PublicInbox/InboxIdle.pm
+++ b/lib/PublicInbox/InboxIdle.pm
@@ -8,13 +8,13 @@ use fields qw(pi_config inot pathmap);
 use Cwd qw(abs_path);
 use Symbol qw(gensym);
 use PublicInbox::Syscall qw(EPOLLIN EPOLLET);
-my $IN_CLOSE = 0x08 | 0x10; # match Linux inotify
+my $IN_MODIFY = 0x02; # match Linux inotify
 my $ino_cls;
 if ($^O eq 'linux' && eval { require Linux::Inotify2; 1 }) {
-	$IN_CLOSE = Linux::Inotify2::IN_CLOSE();
+	$IN_MODIFY = Linux::Inotify2::IN_MODIFY();
 	$ino_cls = 'Linux::Inotify2';
 } elsif (eval { require PublicInbox::KQNotify }) {
-	$IN_CLOSE = PublicInbox::KQNotify::IN_CLOSE();
+	$IN_MODIFY = PublicInbox::KQNotify::NOTE_WRITE();
 	$ino_cls = 'PublicInbox::KQNotify';
 }
 require PublicInbox::In2Tie if $ino_cls;
@@ -39,7 +39,7 @@ sub in2_arm ($$) { # PublicInbox::Config::each_inbox callback
 	$cur->[0] = $ibx;
 
 	my $lock = "$dir/".($ibx->version >= 2 ? 'inbox.lock' : 'ssoma.lock');
-	$cur->[1] = $inot->watch($lock, $IN_CLOSE, sub { $ibx->on_unlock });
+	$cur->[1] = $inot->watch($lock, $IN_MODIFY, sub { $ibx->on_unlock });
 
 	# TODO: detect deleted packs (and possibly other files)
 }
diff --git a/lib/PublicInbox/KQNotify.pm b/lib/PublicInbox/KQNotify.pm
index 1b5c578e..110594cc 100644
--- a/lib/PublicInbox/KQNotify.pm
+++ b/lib/PublicInbox/KQNotify.pm
@@ -8,10 +8,6 @@ use strict;
 use IO::KQueue;
 use PublicInbox::DSKQXS; # wraps IO::KQueue for fork-safe DESTROY
 
-# only true as far as public-inbox is concerned with .lock files:
-sub IN_CLOSE () { NOTE_WRITE }
-#sub IN_CLOSE () { 0x200 } # NOTE_CLOSE_WRITE (FreeBSD 11+ only)
-
 sub new {
 	my ($class) = @_;
 	bless { dskq => PublicInbox::DSKQXS->new, watch => {} }, $class;
@@ -26,7 +22,7 @@ sub watch {
 		EV_ADD | EV_CLEAR, # flags
 		$mask, # fflags
 		0, 0); # data, udata
-	if ($mask == IN_CLOSE) {
+	if ($mask == NOTE_WRITE) {
 		$self->{watch}->{$ident} = [ $fh, $cb ];
 	} else {
 		die "TODO Not implemented: $mask";
@@ -52,7 +48,7 @@ sub poll {
 	for my $kev (@kevents) {
 		my $ident = $kev->[KQ_IDENT];
 		my $mask = $kev->[KQ_FFLAGS];
-		if (($mask & IN_CLOSE) == IN_CLOSE) {
+		if (($mask & NOTE_WRITE) == NOTE_WRITE) {
 			eval { $self->{watch}->{$ident}->[1]->() };
 		}
 	}
diff --git a/lib/PublicInbox/Lock.pm b/lib/PublicInbox/Lock.pm
index 693a3794..c0d4d3b3 100644
--- a/lib/PublicInbox/Lock.pm
+++ b/lib/PublicInbox/Lock.pm
@@ -21,16 +21,12 @@ sub lock_acquire {
 }
 
 sub lock_release {
-	my ($self) = @_;
+	my ($self, $wake) = @_;
 	return unless $self->{lock_path};
 	my $lockfh = delete $self->{lockfh} or croak 'not locked';
 
-	# NetBSD 8.1 and OpenBSD 6.5 (and maybe other versions/*BSDs) lack
-	# NOTE_CLOSE_WRITE from FreeBSD 11+, so trigger NOTE_WRITE, instead.
-	# We also need to change the ctime on Linux systems w/o inotify
-	if ($^O ne 'linux' || !eval { require Linux::Inotify2; 1 }) {
-		syswrite($lockfh, '.');
-	}
+	syswrite($lockfh, '.') if $wake;
+
 	flock($lockfh, LOCK_UN) or die "unlock failed: $!\n";
 	close $lockfh or die "close failed: $!\n";
 }
diff --git a/lib/PublicInbox/SearchIdx.pm b/lib/PublicInbox/SearchIdx.pm
index 00e63938..4caa66d3 100644
--- a/lib/PublicInbox/SearchIdx.pm
+++ b/lib/PublicInbox/SearchIdx.pm
@@ -78,12 +78,12 @@ sub new {
 sub need_xapian ($) { $_[0]->{indexlevel} =~ $xapianlevels }
 
 sub _xdb_release {
-	my ($self) = @_;
+	my ($self, $wake) = @_;
 	if (need_xapian($self)) {
 		my $xdb = delete $self->{xdb} or croak 'not acquired';
 		$xdb->close;
 	}
-	$self->lock_release if $self->{creat};
+	$self->lock_release($wake) if $self->{creat};
 	undef;
 }
 
@@ -800,7 +800,7 @@ sub _index_sync {
 		}
 		$self->commit_txn_lazy;
 		$git->cleanup;
-		$xdb = _xdb_release($self);
+		$xdb = _xdb_release($self, $nr);
 		# let another process do some work... <
 		$pr->("indexed $nr/$self->{ntodo}\n") if $pr && $nr;
 		if (!$newest) {
diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index a0f041dd..567f203c 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -670,6 +670,7 @@ sub barrier { checkpoint($_[0], 1) };
 # public
 sub done {
 	my ($self) = @_;
+	my $nbytes = $self->{transact_bytes};
 	my $im = delete $self->{im};
 	$im->done if $im; # PublicInbox::Import::done
 	checkpoint($self);
@@ -682,7 +683,7 @@ sub done {
 	$self->{over}->disconnect;
 	delete $self->{bnote};
 	$self->{transact_bytes} = 0;
-	$self->lock_release if $shards;
+	$self->lock_release(!!$nbytes) if $shards;
 	$self->{-inbox}->git->cleanup;
 }
 
diff --git a/lib/PublicInbox/Xapcmd.pm b/lib/PublicInbox/Xapcmd.pm
index 337978bd..78414041 100644
--- a/lib/PublicInbox/Xapcmd.pm
+++ b/lib/PublicInbox/Xapcmd.pm
@@ -39,6 +39,7 @@ sub commit_changes ($$$$) {
 			my $tmp_over = "$new/over.sqlite3";
 			$over->connect->sqlite_backup_to_file($tmp_over);
 			$over = undef;
+			syswrite($im->{lockfh}, '.'); # trigger ->check_inodes
 		}
 
 		if (!defined($new)) { # culled shard