For now, we will document this since it allows better
performance without the burden of extensions. Perhaps one day
far in the future Perl can natively support vfork(2) AND that
version of Perl will be widely available, but I suspect that day
is at least a decade away, if not two:
https://rt.perl.org/Ticket/Display.html?id=128227
Used by systemd (and compatible) installations for socket
activation. See L<systemd.socket(5)> and L<sd_listen_fds(3)>.
+=item PERL_INLINE_DIRECTORY
+
+Pointing this to point to a writable directory enables the use
+of L<Inline> and L<Inline::C> extensions which may provide
+platform-specific performance improvements. Currently, this
+enables the use of L<vfork(2)> which speeds up subprocess
+spawning with the Linux kernel.
+
+public-inbox will never enable L<Inline::C> automatically without
+this environment variable set. See L<Inline> and L<Inline::C>
+for more details.
+
=back
=head1 UPGRADING
config file. default: ~/.public-inbox/config
See L<public-inbox-config(5)>
+=item PERL_INLINE_DIRECTORY
+
+This may affect any public-inbox processes, but is intended
+for long-lived ones such as C<public-inbox-watch> or network
+daemons. See L<public-inbox-daemon(8)>.
+
=back
=head1 CONTACT