shrink low-bandwidth pipes under Linux

I've hit /proc/sys/fs/pipe-user-pages-* limits on some systems.
So stop hogging resources on pipes which don't benefit from
giant sizes.

Some of these can use eventfd in the future to further reduce
resource use.

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index 0a304aae..fbab8f70 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -243,6 +243,9 @@ sub idx_init {
 
         if ($self->{parallel}) {
                 pipe(my ($r, $w)) or die "pipe failed: $!";
+                # pipe for barrier notifications doesn't need to be big,
+                # 1031: F_SETPIPE_SZ
+                fcntl($w, 1031, 4096) if $^O eq 'linux';
                 $self->{bnote} = [ $r, $w ];
                 $w->autoflush(1);
         }