[PATCH 02/14] ds: replace FD map hash table with array

[Eric Wong]

FDs are array indices into the kernel, anyways, so we can
take advantage of space savings and speedups because the
majority of FDs a big process has is going to end up in
the array, anyways.
---
 lib/PublicInbox/DS.pm          | 18 +++++++++---------
 lib/PublicInbox/LeiStoreErr.pm |  2 +-
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/lib/PublicInbox/DS.pm b/lib/PublicInbox/DS.pm
index ca1f0f81..8331da95 100644
--- a/lib/PublicInbox/DS.pm
+++ b/lib/PublicInbox/DS.pm
@@ -42,7 +42,7 @@ my $reap_armed;
 my @active; # FDs (or objs) returned by epoll/kqueue
 our (%AWAIT_PIDS, # pid => [ $callback, @args ]
        $cur_runq, # only set inside next_tick
-     %DescriptorMap,             # fd (num) -> PublicInbox::DS object
+     @FD_MAP, # fd (num) -> PublicInbox::DS object
      $Poller, # global Select, Epoll, DSPoll, or DSKQXS ref
 
      @post_loop_do,              # subref + args to call at the end of each 
loop
@@ -74,7 +74,7 @@ sub Reset {
                # clobbering $Poller may call DSKQXS::DESTROY,
                # we must always have this set to something to avoid
                # needing branches before ep_del/ep_mod calls (via ->close).
-               %DescriptorMap = (); # likely to call ep_del
+               @FD_MAP = ();
                @Timers = ();
                %UniqTimer = ();
                @post_loop_do = ();
@@ -85,7 +85,7 @@ sub Reset {
                $nextq = undef; # may call ep_del
                %AWAIT_PIDS = ();
        } while (@Timers || $nextq || keys(%AWAIT_PIDS) ||
-               @active || keys(%DescriptorMap) ||
+               @active || @FD_MAP ||
                @post_loop_do || keys(%UniqTimer) ||
                scalar(@{$cur_runq // []})); # do not vivify cur_runq
 
@@ -226,7 +226,7 @@ sub in_loop () { $in_loop }
 # use inside @post_loop_do, returns number of busy clients
 sub close_non_busy () {
        my $n = 0;
-       for my $s (values %DescriptorMap) {
+       for my $s (grep defined, @FD_MAP) {
                # close as much as possible, early as possible
                ($s->busy ? ++$n : $s->close) if $s->can('busy');
        }
@@ -291,7 +291,7 @@ sub event_loop (;$$) {
                $Poller->ep_wait($timeout, \@active);
 
                # map all FDs to their associated Perl object
-               @active = @DescriptorMap{@active};
+               @active = @FD_MAP[@active];
 
                while (my $obj = shift @active) {
                        $obj->event_step;
@@ -329,10 +329,10 @@ retry:
         }
         die "EPOLL_CTL_ADD $self/$sock/$fd: $!";
     }
-    croak("FD:$fd in use by $DescriptorMap{$fd} (for $self/$sock)")
-        if defined($DescriptorMap{$fd});
+    defined($FD_MAP[$fd]) and
+               croak("BUG: FD:$fd in use by $FD_MAP[$fd] (for $self/$sock)");
 
-    $DescriptorMap{$fd} = $self;
+    $FD_MAP[$fd] = $self;
 }
 
 # for IMAP, NNTP, and POP3 which greet clients upon connect
@@ -366,7 +366,7 @@ sub close {
        # be self-referential closures (sub { $client->close })
        # preventing the object from being destroyed
        delete $self->{wbuf};
-       delete $DescriptorMap{fileno($sock)};
+       $FD_MAP[fileno($sock)] = undef;
 
        !$Poller->ep_del($sock); # stop getting notifications
 }
diff --git a/lib/PublicInbox/LeiStoreErr.pm b/lib/PublicInbox/LeiStoreErr.pm
index fe4af51e..c8bc72b6 100644
--- a/lib/PublicInbox/LeiStoreErr.pm
+++ b/lib/PublicInbox/LeiStoreErr.pm
@@ -47,7 +47,7 @@ sub event_step {
        return ($!{EAGAIN} ? 0 : $self->close) if !defined($n);
        return $self->close if !$n;
        my $printed;
-       for my $lei (values %PublicInbox::DS::DescriptorMap) {
+       for my $lei (grep defined, @PublicInbox::DS::FD_MAP) {
                my $cb = $lei->can('store_path') // next;
                next if $cb->($lei) ne $self->{store_path};
                emit($lei->{2} // next, $buf) and $printed = 1;