[PATCH] daemon: dedupe PublicInbox::Config objects by pathname

[Eric Wong]

This means all Inbox, Git, Over, Msgmap, Search objects also get
deduplicated if they belong to the same config file, reducing
memory and FD usage.  This helps save memory and improve cache
hit rates in -netd setups where NNTP, IMAP, HTTP, and POP3
servers run in the same process.

InboxIdle was the only bit which needed adjustment, but there
may be other bugs lurking despite all tests passing.
---
 Pored over the read-only server code a bit to see if there's
 any problems lurking, but I haven't noticed any...

 lib/PublicInbox/Config.pm    | 9 ++++++++-
 lib/PublicInbox/Daemon.pm    | 3 +++
 lib/PublicInbox/InboxIdle.pm | 4 ++--
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/lib/PublicInbox/Config.pm b/lib/PublicInbox/Config.pm
index a31b5b74..ad8b8e9d 100644
--- a/lib/PublicInbox/Config.pm
+++ b/lib/PublicInbox/Config.pm
@@ -13,6 +13,7 @@ use v5.10.1;
 use PublicInbox::Inbox;
 use PublicInbox::Spawn qw(popen_rd);
 our $LD_PRELOAD = $ENV{LD_PRELOAD}; # only valid at startup
+our $DEDUPE; # set to {} to dedupe or clear cache
 
 sub _array ($) { ref($_[0]) eq 'ARRAY' ? $_[0] : [ $_[0] ] }
 
@@ -22,11 +23,17 @@ sub new {
        my ($class, $file, $errfh) = @_;
        $file //= default_file();
        my $self;
+       my $set_dedupe;
        if (ref($file) eq 'SCALAR') { # used by some tests
                open my $fh, '<', $file or die;  # PerlIO::scalar
                $self = config_fh_parse($fh, "\n", '=');
                bless $self, $class;
        } else {
+               if (-f $file && $DEDUPE) {
+                       $file = rel2abs_collapsed($file);
+                       $self = $DEDUPE->{$file} and return $self;
+                       $set_dedupe = 1;
+               }
                $self = git_config_dump($class, $file, $errfh);
                $self->{'-f'} = $file;
        }
@@ -62,7 +69,7 @@ sub new {
        if (my $css = delete $self->{'publicinbox.css'}) {
                $self->{css} = _array($css);
        }
-
+       $DEDUPE->{$file} = $self if $set_dedupe;
        $self;
 }
 
diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index 86234771..b6f4f9ed 100644
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -22,6 +22,7 @@ use PublicInbox::Sigfd;
 use PublicInbox::Git;
 use PublicInbox::GitAsyncCat;
 use PublicInbox::Eml;
+use PublicInbox::Config;
 our $SO_ACCEPTFILTER = 0x1000;
 my @CMD;
 my ($set_user, $oldset);
@@ -653,8 +654,10 @@ sub defer_accept ($$) {
 
 sub daemon_loop ($) {
        my ($xnetd) = @_;
+       local $PublicInbox::Config::DEDUPE = {}; # enable dedupe cache
        my $refresh = sub {
                my ($sig) = @_;
+               %$PublicInbox::Config::DEDUPE = (); # clear cache
                for my $xn (values %$xnetd) {
                        delete $xn->{tlsd}->{ssl_ctx}; # PublicInbox::TLS::start
                        eval { $xn->{refresh}->($sig) };
diff --git a/lib/PublicInbox/InboxIdle.pm b/lib/PublicInbox/InboxIdle.pm
index 2781b3e1..ffbbfea7 100644
--- a/lib/PublicInbox/InboxIdle.pm
+++ b/lib/PublicInbox/InboxIdle.pm
@@ -30,9 +30,9 @@ sub in2_arm ($$) { # PublicInbox::Config::each_inbox callback
        my $old_ibx = $cur->[0];
        $cur->[0] = $ibx;
        if ($old_ibx) {
-               $ibx->{unlock_subs} and
-                       die "BUG: $dir->{unlock_subs} should not exist";
+               my $u = $ibx->{unlock_subs};
                $ibx->{unlock_subs} = $old_ibx->{unlock_subs};
+               %{$ibx->{unlock_subs}} = (%$u, %{$ibx->{unlock_subs}}) if $u;
 
                # Linux::Inotify2::Watch::name matches if watches are the
                # same, no point in replacing a watch of the same name