[PATCH 2/4] evcleanup: micro-optimize asap function

[Eric Wong]

Instead of relying on a timer with immediate callback,
arm a pipe to watch for writability, ensuring the callback
always fires.
---
 lib/PublicInbox/EvCleanup.pm | 42 +++++++++++++++++++++++++++++++++---------
 1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/lib/PublicInbox/EvCleanup.pm b/lib/PublicInbox/EvCleanup.pm
index 5efb093..61837b8 100644
--- a/lib/PublicInbox/EvCleanup.pm
+++ b/lib/PublicInbox/EvCleanup.pm
@@ -5,32 +5,56 @@
 package PublicInbox::EvCleanup;
 use strict;
 use warnings;
+use base qw(Danga::Socket);
+use fields qw(rd);
+my $singleton;
+my $asapq = [ [], undef ];
+my $laterq = [ [], undef ];
 
-my $asapq = { queue => [], timer => undef };
-my $laterq = { queue => [], timer => undef };
+sub once_init () {
+       my $self = fields::new('PublicInbox::EvCleanup');
+       my ($r, $w);
+       pipe($r, $w) or die "pipe: $!";
+       $self->SUPER::new($w);
+       $self->{rd} = $r; # never read, since we never write..
+       $self;
+}
 
 sub _run_all ($) {
        my ($q) = @_;
 
-       my $run = $q->{queue};
-       $q->{queue} = [];
-       $q->{timer} = undef;
+       my $run = $q->[0];
+       $q->[0] = [];
+       $q->[1] = undef;
        $_->() foreach @$run;
 }
 
 sub _run_asap () { _run_all($asapq) }
 sub _run_later () { _run_all($laterq) }
 
+# Called by Danga::Socket
+sub event_write {
+       my ($self) = @_;
+       $self->watch_write(0);
+       _run_asap();
+}
+
+sub _asap_timer () {
+       $singleton ||= once_init();
+       $singleton->watch_write(1);
+       1;
+}
+
 sub asap ($) {
        my ($cb) = @_;
-       push @{$asapq->{queue}}, $cb;
-       $asapq->{timer} ||= Danga::Socket->AddTimer(0, *_run_asap);
+       push @{$asapq->[0]}, $cb;
+       $asapq->[1] ||= _asap_timer();
 }
 
 sub later ($) {
        my ($cb) = @_;
-       push @{$laterq->{queue}}, $cb;
-       $laterq->{timer} ||= Danga::Socket->AddTimer(60, *_run_later);
+       push @{$laterq->[0]}, $cb;
+       $laterq->[1] ||= Danga::Socket->AddTimer(60, *_run_later);
 }
 
 END {
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