erts: Create forker process for spawn driver

Instead of forking from the beam process, we create a separate
process in which all forks are done. This has several advantages:

1) performance:
  * don't have to close all fd's in the world
  * fork only has to copy stuff from a small process
  * work is done in a completely seperate process
  * a 3x performance increase has been measured,
    can be made even greater (10x) if we cache the
    environment in child setup

2) stability
  * the exec is done in another process than beam, which means that
    if the file that we exec to is on an nfs that is not available
    right now we will not block a scheduler until the nfs returns.

3) simplicity
  * don't have to deal with SIGCHLD in the erts

Unfortunately, this solution also implies some badness.

1) There will always be a seperate process running together with
   beam on unix. This could be confusing and undesirable.
2) We have to transfer the entire environment to child_setup
   for each command.

OTP-13088

1 files changed, 47 insertions, 0 deletions

diff --git a/erts/emulator/sys/unix/sys_uds.h b/erts/emulator/sys/unix/sys_uds.h
new file mode 100644
index 0000000000..7ff58b17dd
--- /dev/null
+++ b/erts/emulator/sys/unix/sys_uds.h
@@ -0,0 +1,47 @@
+/*
+ * %CopyrightBegin%
+ *
+ * Copyright Ericsson AB 2002-2009. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * %CopyrightEnd%
+ */
+
+#ifndef _ERL_UNIX_UDS_H
+#define _ERL_UNIX_UDS_H
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#if defined(__sun__) && !defined(_XOPEN_SOURCE)
+#define _XOPEN_SOURCE 500
+#endif
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+
+#include "sys.h"
+
+int sys_uds_readv(int fd, struct iovec *iov, size_t iov_len,
+                  int *fds, int fd_count, int flags);
+int sys_uds_read(int fd, char *buff, size_t len,
+                 int *fds, int fd_count, int flags);
+int sys_uds_writev(int fd, struct iovec *iov, size_t iov_len,
+                   int *fds, int fd_count, int flags);
+int sys_uds_write(int fd, char *buff, size_t len,
+                  int *fds, int fd_count, int flags);
+
+#endif /* #ifndef _ERL_UNIX_UDS_H */