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The previously used message queue partitioned into two halves has been
replaced by a more general signal queue partitioned into three parts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, 18 insertions, 157 deletions

diff --git a/erts/etc/unix/etp-commands.in b/erts/etc/unix/etp-commands.in
index 02ace9126c..bac90cb472 100644
--- a/erts/etc/unix/etp-commands.in
+++ b/erts/etc/unix/etp-commands.in
@@ -2,7 +2,7 @@
 #
 # %CopyrightBegin%
 # 
-# Copyright Ericsson AB 2005-2017. All Rights Reserved.
+# Copyright Ericsson AB 2005-2018. 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.
@@ -1290,7 +1290,7 @@ document etp-msgq
 % Sequential trace tokens are included in comments and 
 % the current match position in the queue is marked '<='.
 % 
-% A process's message queue is process_tab[i]->msg.
+% A process's message queue is process_tab[i]->sig_qs.
 %---------------------------------------------------------------------------
 end
 
@@ -1693,7 +1693,7 @@ define etp-proc-state-int
     printf "dirty-cpu-proc | "
   end
   if ($arg0 & 0x2000000)
-    printf "GARBAGE<0x2000000> | "
+    printf "sig-q | "
   end
   if ($arg0 & 0x1000000)
     printf "off-heap-msgq | "
@@ -1714,10 +1714,10 @@ define etp-proc-state-int
     printf "active-sys | "
   end
   if ($arg0 & 0x80000)
-    printf "trapping-exit | "
+    printf "sig-in-q | "
   end
   if ($arg0 & 0x40000)
-    printf "GARBAGE<0x40000> | "
+    printf "sys-tasks | "
   end
   if ($arg0 & 0x20000)
     printf "garbage-collecting | "
@@ -1735,7 +1735,7 @@ define etp-proc-state-int
     printf "active | "
   end
   if ($arg0 & 0x1000)
-    printf "pending-exit | "
+    printf "unused | "
   end
   if ($arg0 & 0x800)
     printf "exiting | "
@@ -1819,160 +1819,21 @@ document etp-proc-state
 % Print state of process
 %---------------------------------------------------------------------------
 end
-define etp-proc-state-int
+
+define etp-proc-flags-int
 # Args: int
 #
-  if ($arg0 & 0x80000000)
-    printf "GARBAGE<0x80000000> | "
-  end
-  if ($arg0 & 0x40000000)
-    printf "dirty-running-sys | "
-  end
-  if ($arg0 & 0x20000000)
-    printf "dirty-running | "
-  end
-  if ($arg0 & 0x10000000)
-    printf "dirty-active-sys | "
+  if ($arg0 & ~0xfffffff)
+    printf "GARBAGE<%x> ", ($arg0 & ~0x1ffffff)
   end
   if ($arg0 & 0x8000000)
-    printf "dirty-io-proc | "
+    printf "trap-exit "
   end
   if ($arg0 & 0x4000000)
-    printf "dirty-cpu-proc | "
+    printf "local-sigs-only "
   end
   if ($arg0 & 0x2000000)
-    printf "on-heap-msgq | "
-  end
-  if ($arg0 & 0x1000000)
-    printf "off-heap-msgq | "
-  end
-  if ($arg0 & 0x800000)
-    printf "delayed-sys | "
-  end
-  if ($arg0 & 0x400000)
-    printf "proxy | "
-    set $proxy_process = 1
-  else
-    set $proxy_process = 0
-  end
-  if ($arg0 & 0x200000)
-    printf "running-sys | "
-  end
-  if ($arg0 & 0x100000)
-    printf "active-sys | "
-  end
-  if ($arg0 & 0x80000)
-    printf "trapping-exit | "
-  end
-  if ($arg0 & 0x40000)
-    printf "bound | "
-  end
-  if ($arg0 & 0x20000)
-    printf "garbage-collecting | "
-  end
-  if ($arg0 & 0x10000)
-    printf "suspended | "
-  end
-  if ($arg0 & 0x8000)
-    printf "running | "
-  end
-  if ($arg0 & 0x4000)
-    printf "in-run-queue | "
-  end
-  if ($arg0 & 0x2000)
-    printf "active | "
-  end
-  if ($arg0 & 0x1000)
-    printf "pending-exit | "
-  end
-  if ($arg0 & 0x800)
-    printf "exiting | "
-  end
-  if ($arg0 & 0x400)
-    printf "free | "
-  end
-  if ($arg0 & 0x200)
-    printf "in-prq-low | "
-  end
-  if ($arg0 & 0x100)
-    printf "in-prq-normal | "
-  end
-  if ($arg0 & 0x80)
-    printf "in-prq-high | "
-  end
-  if ($arg0 & 0x40)
-    printf "in-prq-max | "
-  end
-  if ($arg0 & 0x30) == 0x0
-    printf "prq-prio-max | "
-  else
-    if ($arg0 & 0x30) == 0x10
-      printf "prq-prio-high | "
-    else
-      if ($arg0 & 0x30) == 0x20
-        printf "prq-prio-normal | "
-      else
-        printf "prq-prio-low | "
-      end
-    end
-  end
-  if ($arg0 & 0xc) == 0x0
-    printf "usr-prio-max | "
-  else
-    if ($arg0 & 0xc) == 0x4
-      printf "usr-prio-high | "
-    else
-      if ($arg0 & 0xc) == 0x8
-        printf "usr-prio-normal | "
-      else
-        printf "usr-prio-low | "
-      end
-    end
-  end
-  if ($arg0 & 0x3) == 0x0
-    printf "act-prio-max\n"
-  else
-    if ($arg0 & 0x3) == 0x1
-      printf "act-prio-high\n"
-    else
-      if ($arg0 & 0x3) == 0x2
-        printf "act-prio-normal\n"
-      else
-        printf "act-prio-low\n"
-      end
-    end
-  end
-end
-
-document etp-proc-state-int
-%---------------------------------------------------------------------------
-% etp-proc-state-int int
-% 
-% Print state of process state value
-%---------------------------------------------------------------------------
-end
-
-
-define etp-proc-state
-# Args: Process*
-#
-  set $state_int = *(((Uint32 *) &(((Process *) $arg0)->state)))
-  etp-proc-state-int $state_int
-end
-
-document etp-proc-state
-%---------------------------------------------------------------------------
-% etp-proc-state Process*
-% 
-% Print state of process
-%---------------------------------------------------------------------------
-end
-
-define etp-proc-flags-int
-# Args: int
-#
-  if ($arg0 & ~0x1ffffff)
-    printf "GARBAGE<%x> ", ($arg0 & ~0x1ffffff)
+    printf "hibernated "
   end
   if ($arg0 & 0x1000000)
     printf "dirty-minor-gc "
@@ -2131,9 +1992,9 @@ define etp-process-info
   end
   printf "  Mbuf size: %ld\n", $etp_proc->mbuf_sz
   if (etp_smp_compiled)
-    printf "  Msgq len: %ld (inner=%ld, outer=%ld)\n", ($etp_proc->msg.len + $etp_proc->msg_inq.len), $etp_proc->msg.len, $etp_proc->msg_inq.len
+    printf "  Msgq len: %ld (inner=%ld, outer=%ld)\n", ($etp_proc->sig_qs.len + $etp_proc->sig_inq.len), $etp_proc->sig_qs.len, $etp_proc->sig_inq.len
   else
-    printf "  Msgq len: %d\n", $etp_proc->msg.len
+    printf "  Msgq len: %d\n", $etp_proc->sig_qs.len
   end
   printf "  Parent: "
   etp-1 $etp_proc->parent
@@ -2236,9 +2097,9 @@ define etp-process-memory-info
     end
     printf "] [Mbuf: %5ld", $etp_pmem_proc->mbuf_sz
     if (etp_smp_compiled)
-      printf " | %3ld (%3ld | %3ld)", ($etp_pmem_proc->msg.len + $etp_pmem_proc->msg_inq.len), $etp_pmem_proc->msg.len, $etp_pmem_proc->msg_inq.len
+      printf " | %3ld (%3ld | %3ld)", ($etp_pmem_proc->sig_qs.len + $etp_pmem_proc->sig_inq.len), $etp_pmem_proc->sig_qs.len, $etp_pmem_proc->sig_inq.len
     else
-      printf " | %3ld", $etp_pmem_proc->msg.len
+      printf " | %3ld", $etp_pmem_proc->sig_qs.len
     end
     printf "] "
     if ($etp_pmem_proc->i)
@@ -3696,7 +3557,7 @@ define etp-chart
 # Non-reentrant
   etp-chart-start ($arg0)
   set ($arg0) = ($arg0)
-  etp-msgq (($arg0)->msg)
+  etp-msgq (($arg0)->sig_qs)
   etp-stackdump ($arg0)
   etp-dictdump (($arg0)->dictionary)
   etp-dictdump (($arg0)->debug_dictionary)