erts: Optimize spawn driver for large(r) environments

that need to be enqueued.

1 files changed, 7 insertions, 2 deletions

diff --git a/erts/emulator/sys/unix/sys_drivers.c b/erts/emulator/sys/unix/sys_drivers.c
index 812112fb91..e08ef41817 100644
--- a/erts/emulator/sys/unix/sys_drivers.c
+++ b/erts/emulator/sys/unix/sys_drivers.c
@@ -765,9 +765,14 @@ static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
         if (res < (buffsz + sizeof(buffsz))) {
             /* we only wrote part of the command payload. Enqueue the rest. */
             for (i = 0; i < iov_len; i++) {
-                driver_enq(port_num, io_vector[i].iov_base, io_vector[i].iov_len);
+                if (res >= io_vector[i].iov_len)
+                    res -= io_vector[i].iov_len;
+                else {
+                    driver_enq(port_num, io_vector[i].iov_base + res,
+                               io_vector[i].iov_len - res);
+                    res = 0;
+                }
             }
-            driver_deq(port_num, res);
             driver_select(port_num, ofd[1], ERL_DRV_WRITE|ERL_DRV_USE, 1);
         }