MANIFEST                      |  1 +
 lib/PublicInbox/Config.pm     | 18 ------------------
 lib/PublicInbox/ConfigIter.pm | 28 ++++++++++++++++++++++++++++
 lib/PublicInbox/IMAPD.pm      |  6 ++++--

diff --git a/MANIFEST b/MANIFEST
index 0e225b6a99ed65d7dc08a59131b4e9a741ac4e51..04a3744f9cc8a3a7d251e1ddf7cd9ffe5dfdfc90 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -107,6 +107,7 @@ lib/PublicInbox/AltId.pm
 lib/PublicInbox/Cgit.pm
 lib/PublicInbox/CompressNoop.pm
 lib/PublicInbox/Config.pm
+lib/PublicInbox/ConfigIter.pm
 lib/PublicInbox/ContentHash.pm
 lib/PublicInbox/DS.pm
 lib/PublicInbox/DSKQXS.pm
diff --git a/lib/PublicInbox/Config.pm b/lib/PublicInbox/Config.pm
index f78115b6e47b62c91f73b1d1599023774176de39..8ccf337dc0071c4c409567be4a43a239c357984d 100644
--- a/lib/PublicInbox/Config.pm
+++ b/lib/PublicInbox/Config.pm
@@ -99,24 +99,6 @@ 		$cb->($ibx, @arg);
 	}
 }
 
-sub iterate_start {
-	my ($self, $cb, @arg) = @_;
-	my $i = 0;
-	$self->{-iter} = [ \$i, $cb, @arg ];
-}
-
-# for PublicInbox::DS::next_tick, we only call this is if
-# PublicInbox::DS is already loaded
-sub event_step {
-	my ($self) = @_;
-	my ($i, $cb, @arg) = @{$self->{-iter}};
-	my $section = $self->{-section_order}->[$$i++];
-	delete($self->{-iter}) unless defined($section);
-	eval { $cb->($self, $section, @arg) };
-	warn "E: $@ in ${self}::event_step" if $@;
-	PublicInbox::DS::requeue($self) if defined($section);
-}
-
 sub lookup_newsgroup {
 	my ($self, $ng) = @_;
 	_lookup_fill($self, '-by_newsgroup', lc($ng));
diff --git a/lib/PublicInbox/ConfigIter.pm b/lib/PublicInbox/ConfigIter.pm
new file mode 100644
index 0000000000000000000000000000000000000000..26cc70e28ce5094254a0df4c1e518fe603cb1c04
--- /dev/null
+++ b/lib/PublicInbox/ConfigIter.pm
@@ -0,0 +1,28 @@
+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# Intended for PublicInbox::DS->EventLoop in read-only daemons
+# to avoid each_inbox() monopolizing the event loop when hundreds/thousands
+# of inboxes are in play.
+package PublicInbox::ConfigIter;
+use strict;
+use v5.10.1;
+
+sub new {
+	my ($class, $pi_cfg, $cb, @args) = @_;
+	my $i = 0;
+	bless [ $pi_cfg, \$i, $cb, @args ], __PACKAGE__;
+}
+
+# for PublicInbox::DS::next_tick, we only call this is if
+# PublicInbox::DS is already loaded
+sub event_step {
+	my $self = shift;
+	my ($pi_cfg, $i, $cb, @arg) = @$self;
+	my $section = $pi_cfg->{-section_order}->[$$i++];
+	eval { $cb->($pi_cfg, $section, @arg) };
+	warn "E: $@ in ${self}::event_step" if $@;
+	PublicInbox::DS::requeue($self) if defined($section);
+}
+
+1;
diff --git a/lib/PublicInbox/IMAPD.pm b/lib/PublicInbox/IMAPD.pm
index 09bedf5ca9b42c7b74129a94bab7b50b5df0acc3..3c211ee1bf111568b70040c2b97559f9a88c7580 100644
--- a/lib/PublicInbox/IMAPD.pm
+++ b/lib/PublicInbox/IMAPD.pm
@@ -6,6 +6,7 @@ # see script/public-inbox-imapd for how it is used
 package PublicInbox::IMAPD;
 use strict;
 use PublicInbox::Config;
+use PublicInbox::ConfigIter;
 use PublicInbox::InboxIdle;
 use PublicInbox::IMAP;
 use PublicInbox::DummyInbox;
@@ -98,8 +99,9 @@ 	my ($self, $sig) = @_;
 	my $pi_config = PublicInbox::Config->new;
 	if ($sig) { # SIGHUP is handled through the event loop
 		$self->{imapd_next} = { dummies => {}, mailboxes => {} };
-		$pi_config->iterate_start(\&imapd_refresh_step, $self);
-		PublicInbox::DS::requeue($pi_config); # call event_step
+		my $iter = PublicInbox::ConfigIter->new($pi_config,
+						\&imapd_refresh_step, $self);
+		$iter->event_step;
 	} else { # initial start is synchronous
 		$self->{dummies} = {};
 		$pi_config->each_inbox(\&imapd_refresh_ibx, $self);