Implementation of true asynchronous signaling between processes

Communication between Erlang processes has conceptually always been
performed through asynchronous signaling. The runtime system
implementation has however previously preformed most operation
synchronously. In a system with only one true thread of execution, this
is not problematic (often the opposite). In a system with multiple threads
of execution (as current runtime system implementation with SMP support)
it becomes problematic. This since it often involves locking of structures
when updating them which in turn cause resource contention. Utilizing
true asynchronous communication often avoids these resource contention
issues.

The case that triggered this change was contention on the link lock due
to frequent updates of the monitor trees during communication with a
frequently used server. The signal order delivery guarantees of the
language makes it hard to change the implementation of only some signals
to use true asynchronous signaling. Therefore the implementations
of (almost) all signals have been changed.

Currently the following signals have been implemented as true
asynchronous signals:
- Message signals
- Exit signals
- Monitor signals
- Demonitor signals
- Monitor triggered signals (DOWN, CHANGE, etc)
- Link signals
- Unlink signals
- Group leader signals

All of the above already defined as asynchronous signals in the
language. The implementation of messages signals was quite
asynchronous to begin with, but had quite strict delivery constraints
due to the ordering guarantees of signals between a pair of processes.

The previously used message queue partitioned into two halves has been
replaced by a more general signal queue partitioned into three parts
that service all kinds of signals. More details regarding the signal
queue can be found in comments in the erl_proc_sig_queue.h file.

The monitor and link implementations have also been completely replaced
in order to fit the new asynchronous signaling implementation as good
as possible. More details regarding the new monitor and link
implementations can be found in the erl_monitor_link.h file.

1 files changed, 10 insertions, 5 deletions

diff --git a/erts/emulator/beam/erl_alloc.types b/erts/emulator/beam/erl_alloc.types
index 8107f133aa..4a6a19b210 100644
--- a/erts/emulator/beam/erl_alloc.types
+++ b/erts/emulator/beam/erl_alloc.types
@@ -1,7 +1,7 @@
 #
 # %CopyrightBegin%
 #
-# Copyright Ericsson AB 2003-2017. All Rights Reserved.
+# Copyright Ericsson AB 2003-2018. 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.
@@ -282,6 +282,11 @@ type	THR_PRGR_IDATA	LONG_LIVED	SYSTEM		thr_prgr_internal_data
 type	THR_PRGR_DATA	LONG_LIVED	SYSTEM		thr_prgr_data
 type	T_THR_PRGR_DATA	SHORT_LIVED	SYSTEM		temp_thr_prgr_data
 type	RELEASE_LAREA	SHORT_LIVED	SYSTEM		release_literal_area
+type	SIG_DATA	SHORT_LIVED	PROCESSES	signal_data
+type	DIST_DEMONITOR	SHORT_LIVED	PROCESSES	dist_demonitor
+type	CML_CLEANUP	SHORT_LIVED	SYSTEM		connection_ml_cleanup
+type	ML_YIELD_STATE	SHORT_LIVED	SYSTEM		monitor_link_yield_state
+type	ML_DIST		STANDARD	SYSTEM		monitor_link_dist
 
 type	ENVIRONMENT	SYSTEM		SYSTEM		environment
 
@@ -326,8 +331,8 @@ type    LCNT_VECTOR SHORT_LIVED SYSTEM lcnt_sample_vector
 type	DEBUG	        SHORT_LIVED	SYSTEM          debugging
 
 type	DDLL_PROCESS	STANDARD	SYSTEM		ddll_processes
-type	MONITOR_LH	STANDARD	PROCESSES	monitor_lh
-type	NLINK_LH	STANDARD	PROCESSES	nlink_lh
+type	MONITOR_EXT	STANDARD	PROCESSES	monitor_extended
+type	LINK_EXT	STANDARD	PROCESSES	link_extended
 type	CODE		LONG_LIVED	CODE		code
 type	LITERAL		LITERAL 	CODE		literal
 type	LITERAL_REF	SHORT_LIVED	CODE		literal_area_ref
@@ -340,8 +345,8 @@ type  	LL_TEMP_TERM 	LONG_LIVED	SYSTEM		ll_temp_term
 type	NIF_TRAP_EXPORT	STANDARD	PROCESSES	nif_trap_export_entry
 type	NIF_EXP_TRACE	FIXED_SIZE	PROCESSES	nif_export_trace
 type	EXPORT		LONG_LIVED	CODE		export_entry
-type	MONITOR_SH	FIXED_SIZE	PROCESSES	monitor_sh
-type	NLINK_SH	FIXED_SIZE	PROCESSES	nlink_sh
+type	MONITOR		FIXED_SIZE	PROCESSES	monitor
+type	LINK		FIXED_SIZE	PROCESSES	link
 type	AINFO_REQ	SHORT_LIVED	SYSTEM		alloc_info_request
 type	SCHED_WTIME_REQ	SHORT_LIVED	SYSTEM		sched_wall_time_request
 type	GC_INFO_REQ	SHORT_LIVED	SYSTEM		gc_info_request