daemon: use SSL_MODE_RELEASE_BUFFERS

34K per idle connection adds up to large amounts of memory;
especially with the speed of malloc nowadays compared to the
cost of cache misses or worse, swapping.

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index 55103f40..c4481555 100644
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -59,6 +59,16 @@ sub accept_tls_opt ($) {
         }
         my $ctx = IO::Socket::SSL::SSL_Context->new(%ctx_opt) or
                 die 'SSL_Context->new: '.PublicInbox::TLS::err();
+
+        # save ~34K per idle connection (cf. SSL_CTX_set_mode(3ssl))
+        # RSS goes from 346MB to 171MB with 10K idle NNTPS clients on amd64
+        # cf. https://rt.cpan.org/Ticket/Display.html?id=129463
+        my $mode = eval { Net::SSLeay::MODE_RELEASE_BUFFERS() };
+        if ($mode && $ctx->{context}) {
+                eval { Net::SSLeay::CTX_set_mode($ctx->{context}, $mode) };
+                warn "W: $@ (setting SSL_MODE_RELEASE_BUFFERS)\n" if $@;
+        }
+
         { SSL_server => 1, SSL_startHandshake => 0, SSL_reuse_ctx => $ctx };
 }