erts: Move fds with active true behaviour to own pollset

At start of the VM a poll-set that the schedulers
will check is created where fds that have triggered
many (at the moment, many means 10) times without
being deselected inbetween. In this scheduler specific
poll-set fds do not use ONESHOT, which means that the
number of syscalls goes down dramatically for such fds.

This pollset is introduced in order to handle fds that
are used by the erlang distribution and that never
change their state from {active, true}.

This pollset only handles ready_input events,
ready_output is still handled by the poll threads.

During overload, polling the scheduler poll-set is done
on a 10ms timer.

1 files changed, 19 insertions, 2 deletions

diff --git a/erts/emulator/beam/erl_port_task.h b/erts/emulator/beam/erl_port_task.h
index ae78a7d8a3..ca5183b305 100644
--- a/erts/emulator/beam/erl_port_task.h
+++ b/erts/emulator/beam/erl_port_task.h
@@ -38,6 +38,8 @@ typedef erts_atomic_t ErtsPortTaskHandle;
 #ifndef ERL_PORT_TASK_H__
 #define ERL_PORT_TASK_H__
 
+#include "erl_poll.h"
+
 #undef ERTS_INCLUDE_SCHEDULER_INTERNALS
 #if (defined(ERL_PROCESS_C__) \
      || defined(ERL_PORT_TASK_C__) \
@@ -54,8 +56,8 @@ typedef erts_atomic_t ErtsPortTaskHandle;
 #define ERTS_PT_FLG_BAD_OUTPUT		(1 << 4)
 
 typedef enum {
-    ERTS_PORT_TASK_INPUT,
-    ERTS_PORT_TASK_OUTPUT,
+    ERTS_PORT_TASK_INPUT = 0,
+    ERTS_PORT_TASK_OUTPUT = 1,
     ERTS_PORT_TASK_TIMEOUT,
     ERTS_PORT_TASK_DIST_CMD,
     ERTS_PORT_TASK_PROC_SIG
@@ -134,6 +136,12 @@ ERTS_GLB_INLINE void erts_port_task_sched_unlock(ErtsPortTaskSched *ptsp);
 ERTS_GLB_INLINE int erts_port_task_sched_lock_is_locked(ErtsPortTaskSched *ptsp);
 ERTS_GLB_INLINE void erts_port_task_sched_enter_exiting_state(ErtsPortTaskSched *ptsp);
 
+#if defined(ERTS_INCLUDE_SCHEDULER_INTERNALS) && ERTS_POLL_USE_SCHEDULER_POLLING
+ERTS_GLB_INLINE int erts_port_task_have_outstanding_io_tasks(void);
+/* NOTE: Do not access any of the exported variables directly */
+extern erts_atomic_t erts_port_task_outstanding_io_tasks;
+#endif
+
 #if ERTS_GLB_INLINE_INCL_FUNC_DEF
 
 ERTS_GLB_INLINE void
@@ -211,6 +219,15 @@ erts_port_task_sched_enter_exiting_state(ErtsPortTaskSched *ptsp)
     erts_atomic32_read_bor_nob(&ptsp->flags, ERTS_PTS_FLG_EXITING);
 }
 
+#if defined(ERTS_INCLUDE_SCHEDULER_INTERNALS) && ERTS_POLL_USE_SCHEDULER_POLLING
+ERTS_GLB_INLINE int
+erts_port_task_have_outstanding_io_tasks(void)
+{
+    return (erts_atomic_read_acqb(&erts_port_task_outstanding_io_tasks)
+	    != 0);
+}
+#endif
+
 #endif
 
 #ifdef ERTS_INCLUDE_SCHEDULER_INTERNALS