Create better distribution of files over async threads

The actual port id is used to create a key from the
pointer value which is the ErlDrvPort. To do this
a new driver api function driver_async_port_key is
added and the driver API minor version is updated.

The documentation is updated and the faulty description of
how to spread ports over async threads is updated to
use the new API.

Testcase also added.

1 files changed, 2 insertions, 1 deletions

diff --git a/erts/emulator/drivers/common/efile_drv.c b/erts/emulator/drivers/common/efile_drv.c
index 779ecd1bd2..c997fe1bf9 100644
--- a/erts/emulator/drivers/common/efile_drv.c
+++ b/erts/emulator/drivers/common/efile_drv.c
@@ -772,6 +772,7 @@ file_init(void)
     return 0;
 }
 
+
 /*********************************************************************
  * Driver entry point -> start
  */
@@ -788,7 +789,7 @@ file_start(ErlDrvPort port, char* command)
     }
     desc->fd = FILE_FD_INVALID;
     desc->port = port;
-    desc->key = (unsigned int) (UWord) port;
+    desc->key = driver_async_port_key(port);
     desc->flags = 0;
     desc->invoke = NULL;
     desc->d = NULL;