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* [PATCH 6/7] ipc: switch to one-way pipes
  2021-01-03  2:06  7% [PATCH 0/7] v2: swap in new IPC package Eric Wong
@ 2021-01-03  2:06  5% ` Eric Wong
  0 siblings, 0 replies; 2+ results
From: Eric Wong @ 2021-01-03  2:06 UTC (permalink / raw)
  To: meta

This fixes a performance regression in multi-process v2 indexing
due to the switch to PublicInbox::IPC.  While Unix sockets are
fewer FDs to manage, pipes allow unprivileged processes to use
larger buffers (up to 1M) on out-of-the-box Linux instances.

A larger buffer via F_SETPIPE_SZ afforded by pipes was proven
valuable during v2 development in 2018 and continues to be
valuable when we get significant amounts of one-way traffic from
the producer parent to worker children.

Compression may be an option for systems without F_SETPIPE_SZ;
but it increases CPU usage with no memory bandwidth savings on
hosts where larger buffers are available.
---
 lib/PublicInbox/IPC.pm            | 115 +++++++++++++++++-------------
 lib/PublicInbox/SearchIdxShard.pm |  23 +++---
 lib/PublicInbox/V2Writable.pm     |   2 +-
 3 files changed, 78 insertions(+), 62 deletions(-)

diff --git a/lib/PublicInbox/IPC.pm b/lib/PublicInbox/IPC.pm
index 6b7b3c7a..c1f6f920 100644
--- a/lib/PublicInbox/IPC.pm
+++ b/lib/PublicInbox/IPC.pm
@@ -6,7 +6,6 @@
 package PublicInbox::IPC;
 use strict;
 use v5.10.1;
-use Socket qw(AF_UNIX SOCK_STREAM);
 use Carp qw(confess croak);
 use PublicInbox::Sigfd;
 my ($enc, $dec);
@@ -34,39 +33,42 @@ if ($enc && $dec) { # should be custom ops
 }
 
 sub _get_rec ($) {
-	my ($sock) = @_;
-	local $/ = "\n";
-	defined(my $len = <$sock>) or return;
+	my ($r) = @_;
+	defined(my $len = <$r>) or return;
 	chop($len) eq "\n" or croak "no LF byte in $len";
-	defined(my $r = read($sock, my $buf, $len)) or croak "read error: $!";
-	$r == $len or croak "short read: $r != $len";
+	defined(my $n = read($r, my $buf, $len)) or croak "read error: $!";
+	$n == $len or croak "short read: $n != $len";
 	thaw($buf);
 }
 
 sub _send_rec ($$) {
-	my ($sock, $ref) = @_;
+	my ($w, $ref) = @_;
 	my $buf = freeze($ref);
-	print $sock length($buf), "\n", $buf or croak "print: $!";
+	print $w length($buf), "\n", $buf or croak "print: $!";
 }
 
 sub ipc_return ($$$) {
-	my ($s2, $ret, $exc) = @_;
-	_send_rec($s2, $exc ? bless(\$exc, 'PublicInbox::IPC::Die') : $ret);
+	my ($w, $ret, $exc) = @_;
+	_send_rec($w, $exc ? bless(\$exc, 'PublicInbox::IPC::Die') : $ret);
 }
 
-sub ipc_worker_loop ($$) {
-	my ($self, $s2) = @_;
-	while (my $rec = _get_rec($s2)) {
-		my ($wantarray, $sub, @args) = @$rec;
-		if (!defined($wantarray)) { # no waiting if client doesn't care
+sub ipc_worker_loop ($$$) {
+	my ($self, $r_req, $w_res) = @_;
+	my ($rec, $wantarray, $sub, @args);
+	local $/ = "\n";
+	while ($rec = _get_rec($r_req)) {
+		($wantarray, $sub, @args) = @$rec;
+		# no waiting if client doesn't care,
+		# this is the overwhelmingly likely case
+		if (!defined($wantarray)) {
 			eval { $self->$sub(@args) };
-			eval { warn "die: $@ (from nowait $sub)\n" } if $@;
+			eval { warn "$$ die: $@ (from nowait $sub)\n" } if $@;
 		} elsif ($wantarray) {
 			my @ret = eval { $self->$sub(@args) };
-			ipc_return($s2, \@ret, $@);
-		} else {
+			ipc_return($w_res, \@ret, $@);
+		} else { # '' => wantscalar
 			my $ret = eval { $self->$sub(@args) };
-			ipc_return($s2, \$ret, $@);
+			ipc_return($w_res, \$ret, $@);
 		}
 	}
 }
@@ -75,33 +77,34 @@ sub ipc_worker_loop ($$) {
 sub ipc_worker_spawn {
 	my ($self, $ident, $oldset) = @_;
 	return unless $enc; # no Sereal or Storable
-	my $pid = $self->{-ipc_worker_pid};
-	confess "BUG: already spawned PID:$pid" if $pid;
-	confess "BUG: already have worker socket" if $self->{-ipc_sock};
-	my ($s1, $s2);
-	socketpair($s1, $s2, AF_UNIX, SOCK_STREAM, 0) or die "socketpair: $!";
+	return if ($self->{-ipc_ppid} // -1) == $$; # idempotent
+	delete(@$self{qw(-ipc_req -ipc_res -ipc_ppid -ipc_pid)});
+	pipe(my ($r_req, $w_req)) or die "pipe: $!";
+	pipe(my ($r_res, $w_res)) or die "pipe: $!";
 	my $sigset = $oldset // PublicInbox::Sigfd::block_signals();
 	my $parent = $$;
 	$self->ipc_atfork_parent;
-	defined($pid = fork) or die "fork: $!";
+	defined(my $pid = fork) or die "fork: $!";
 	if ($pid == 0) {
 		eval { PublicInbox::DS->Reset };
 		$self->{-ipc_parent_pid} = $parent;
-		close $s1 or die "close(\$s1): $!";
-		$s2->autoflush(1);
+		$w_req = $r_res = undef;
+		$w_res->autoflush(1);
 		$SIG{$_} = 'IGNORE' for (qw(TERM INT QUIT));
 		local $0 = $ident;
 		PublicInbox::Sigfd::sig_setmask($oldset);
 		my $on_destroy = $self->ipc_atfork_child;
-		eval { ipc_worker_loop($self, $s2) };
+		eval { ipc_worker_loop($self, $r_req, $w_res) };
 		die "worker $ident PID:$$ died: $@\n" if $@;
 		exit;
 	}
 	PublicInbox::Sigfd::sig_setmask($sigset) unless $oldset;
-	close $s2 or die "close(\$s2): $!";
-	$s1->autoflush(1);
-	$self->{-ipc_sock} = $s1;
-	$self->{-ipc_worker_pid} = $pid;
+	$r_req = $w_res = undef;
+	$w_req->autoflush(1);
+	$self->{-ipc_req} = $w_req;
+	$self->{-ipc_res} = $r_res;
+	$self->{-ipc_ppid} = $$;
+	$self->{-ipc_pid} = $pid;
 }
 
 sub ipc_worker_reap { # dwaitpid callback
@@ -122,15 +125,18 @@ sub ipc_worker_exit {
 # idempotent, can be called regardless of whether worker is active or not
 sub ipc_worker_stop {
 	my ($self) = @_;
-	my $pid;
-	my $s1 = delete $self->{-ipc_sock} or do {
-		$pid = delete $self->{-ipc_worker_pid} and
-			die "unexpected PID:$pid without ipc_sock";
-		return;
-	};
-	$pid = delete $self->{-ipc_worker_pid} or die "no PID?";
-	_send_rec($s1, [ undef, 'ipc_worker_exit', 0 ]);
-	shutdown($s1, 2) or die "shutdown(\$s1) for PID:$pid";
+	my ($pid, $ppid) = delete(@$self{qw(-ipc_pid -ipc_ppid)});
+	my ($w_req, $r_res) = delete(@$self{qw(-ipc_req -ipc_res)});
+	if (!$w_req && !$r_res) {
+		die "unexpected PID:$pid without IPC pipes" if $pid;
+		return; # idempotent
+	}
+	die 'no PID with IPC pipes' unless $pid;
+	_send_rec($w_req, [ undef, 'ipc_worker_exit', 0 ]);
+	$w_req = $r_res = undef;
+
+	# allow any sibling to send ipc_worker_exit, but siblings can't wait
+	return if $$ != $ppid;
 	eval {
 		my $reap = $self->can('ipc_worker_reap');
 		PublicInbox::DS::dwaitpid($pid, $reap, $self);
@@ -153,17 +159,30 @@ sub ipc_lock_init {
 # call $self->$sub(@args), on a worker if ipc_worker_spawn was used
 sub ipc_do {
 	my ($self, $sub, @args) = @_;
-	if (my $s1 = $self->{-ipc_sock}) {
+	if (my $w_req = $self->{-ipc_req}) { # run in worker
 		my $ipc_lock = $self->{-ipc_lock};
 		my $lock = $ipc_lock ? $ipc_lock->lock_for_scope : undef;
-		_send_rec($s1, [ wantarray, $sub, @args ]);
-		return unless defined(wantarray);
-		my $ret = _get_rec($s1) // die "no response on $sub";
-		die $$ret if ref($ret) eq 'PublicInbox::IPC::Die';
-		wantarray ? @$ret : $$ret;
-	} else {
+		if (defined(wantarray)) {
+			my $r_res = $self->{-ipc_res} or die 'no ipc_res';
+			_send_rec($w_req, [ wantarray, $sub, @args ]);
+			my $ret = _get_rec($r_res) // die "no response on $sub";
+			die $$ret if ref($ret) eq 'PublicInbox::IPC::Die';
+			wantarray ? @$ret : $$ret;
+		} else { # likely, fire-and-forget into pipe
+			_send_rec($w_req, [ undef , $sub, @args ]);
+		}
+	} else { # run locally
 		$self->$sub(@args);
 	}
 }
 
+# needed when there's multiple IPC workers and the parent forking
+# causes newer siblings to inherit older siblings sockets
+sub ipc_sibling_atfork_child {
+	my ($self) = @_;
+	my ($pid, undef) = delete(@$self{qw(-ipc_pid -ipc_ppid)});
+	delete(@$self{qw(-ipc_req -ipc_res)});
+	$pid == $$ and die "BUG: $$ ipc_atfork_child called on itself";
+}
+
 1;
diff --git a/lib/PublicInbox/SearchIdxShard.pm b/lib/PublicInbox/SearchIdxShard.pm
index 83cbbb25..0051df93 100644
--- a/lib/PublicInbox/SearchIdxShard.pm
+++ b/lib/PublicInbox/SearchIdxShard.pm
@@ -21,6 +21,14 @@ sub new {
 	if ($v2w->{parallel}) {
 		local $self->{-v2w_afc} = $v2w;
 		$self->ipc_worker_spawn("shard[$shard]");
+		# F_SETPIPE_SZ = 1031 on Linux; increasing the pipe size for
+		# inputs speeds V2Writable batch imports across 8 cores by
+		# nearly 20%.  Since any of our responses are small, make
+		# the response pipe as small as possible
+		if ($^O eq 'linux') {
+			fcntl($self->{-ipc_req}, 1031, 1048576);
+			fcntl($self->{-ipc_res}, 1031, 4096);
+		}
 	}
 	$self;
 }
@@ -36,7 +44,7 @@ sub _worker_done {
 sub ipc_atfork_child { # called automatically before ipc_worker_loop
 	my ($self) = @_;
 	my $v2w = delete $self->{-v2w_afc} or die 'BUG: {-v2w_afc} missing';
-	$v2w->atfork_child; # calls shard_atfork_child on our siblings
+	$v2w->atfork_child; # calls ipc_sibling_atfork_child on our siblings
 	$v2w->{current_info} = "[$self->{shard}]"; # for $SIG{__WARN__}
 	$self->begin_txn_lazy;
 	# caller must capture this:
@@ -49,17 +57,6 @@ sub index_eml {
 	$self->ipc_do('add_message', $eml, $smsg);
 }
 
-# needed when there's multiple IPC workers and the parent forking
-# causes newer siblings to inherit older siblings sockets
-sub shard_atfork_child {
-	my ($self) = @_;
-	my $pid = delete($self->{-ipc_worker_pid}) or
-			die "BUG: $$ no -ipc_worker_pid";
-	my $s1 = delete($self->{-ipc_sock}) or die "BUG: $$ no -ipc_sock";
-	$pid == $$ and die "BUG: $$ shard_atfork_child called on itself";
-	close($s1) or die "close -ipc_sock: $!";
-}
-
 # wait for return to determine when ipc_do('commit_txn_lazy') is done
 sub echo {
 	shift;
@@ -80,7 +77,7 @@ sub shard_close {
 
 sub shard_over_check {
 	my ($self, $over) = @_;
-	if ($self->{-ipc_sock} && $over->{dbh}) {
+	if ($self->{-ipc_req} && $over->{dbh}) {
 		# can't send DB handles over IPC
 		$over = ref($over)->new($over->{dbh}->sqlite_db_filename);
 	}
diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index c4efbdd2..6be95979 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -823,7 +823,7 @@ sub content_exists ($$$) {
 sub atfork_child {
 	my ($self) = @_;
 	if (my $older_siblings = $self->{idx_shards}) {
-		$_->shard_atfork_child for @$older_siblings;
+		$_->ipc_sibling_atfork_child for @$older_siblings;
 	}
 	if (my $im = $self->{im}) {
 		$im->atfork_child;

^ permalink raw reply related	[relevance 5%]

* [PATCH 0/7] v2: swap in new IPC package
@ 2021-01-03  2:06  7% Eric Wong
  2021-01-03  2:06  5% ` [PATCH 6/7] ipc: switch to one-way pipes Eric Wong
  0 siblings, 1 reply; 2+ results
From: Eric Wong @ 2021-01-03  2:06 UTC (permalink / raw)
  To: meta

SearchIdxShard was too big and adding the new extindex
stuff made things worse.  Since I intend to use IPC
in more places, I figured it'd be good to prove it with
works well by dropping it into the old v2 mix.

The below diffstat is nice

Eric Wong (7):
  ipc: some documentation comments
  searchidxshard: use PublicInbox::IPC to kill lots of code
  searchidxshard: IPC conversion, part 2
  searchidxshard: replace index_raw with index_eml
  use Eml (or MIME) objects for all indexing paths
  ipc: switch to one-way pipes
  searchidxshard: use add_xapian directly for v2

 lib/PublicInbox/ExtSearchIdx.pm   |  38 +++--
 lib/PublicInbox/IPC.pm            | 127 +++++++++------
 lib/PublicInbox/Import.pm         |   4 +-
 lib/PublicInbox/LeiStore.pm       |  18 +--
 lib/PublicInbox/SearchIdx.pm      |  35 +---
 lib/PublicInbox/SearchIdxShard.pm | 257 +++++-------------------------
 lib/PublicInbox/Smsg.pm           |  13 ++
 lib/PublicInbox/V2Writable.pm     | 102 +++++-------
 t/import.t                        |  12 +-
 t/search.t                        |   2 +-
 10 files changed, 206 insertions(+), 402 deletions(-)

^ permalink raw reply	[relevance 7%]

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