initial spawn implementation using vfork

Under Linux, vfork maintains constant performance as
parent process size increases.  fork needs to prepare pages
for copy-on-write, requiring a linear scan of the address
space.

1 files changed, 33 insertions, 0 deletions

diff --git a/lib/PublicInbox/SpawnPP.pm b/lib/PublicInbox/SpawnPP.pm
new file mode 100644
index 00000000..ae552dd8
--- /dev/null
+++ b/lib/PublicInbox/SpawnPP.pm
@@ -0,0 +1,33 @@
+# Copyright (C) 2016 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+package PublicInbox::SpawnPP;
+use strict;
+use warnings;
+use POSIX qw(dup2);
+
+# Pure Perl implementation for folks that do not use Inline::C
+sub public_inbox_fork_exec ($$$$$$) {
+        my ($in, $out, $err, $f, $cmd, $env) = @_;
+        my $pid = fork;
+        if ($pid == 0) {
+                if ($in != 0) {
+                        dup2($in, 0) or die "dup2 failed for stdin: $!";
+                }
+                if ($out != 1) {
+                        dup2($out, 1) or die "dup2 failed for stdout: $!";
+                }
+                if ($err != 2) {
+                        dup2($err, 2) or die "dup2 failed for stderr$!";
+                }
+                %ENV = ();
+                foreach my $e (@$env) {
+                        my ($k, $v) = split('=', $e, 2);
+                        $ENV{$k} = $v;
+                }
+                exec @$cmd;
+                exit 1;
+        }
+        $pid;
+}
+
+1;