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authorRickard Green <[email protected]>2018-03-07 01:17:21 +0100
committerRickard Green <[email protected]>2018-03-21 10:27:03 +0100
commit4bc282d812cc2c49aa3e2d073e96c720f16aa270 (patch)
treea7b00cd079368590dc09f62a4d5402be157462ca /erts/emulator/beam/msg_instrs.tab
parent348a4e057db36fac13f1551c0a1c17f0d376da48 (diff)
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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 The previously used message queue partitioned into two halves has been replaced by a more general signal queue partitioned into three parts that service all kinds of signals.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.
Diffstat (limited to 'erts/emulator/beam/msg_instrs.tab')
-rw-r--r--erts/emulator/beam/msg_instrs.tab95
1 files changed, 53 insertions, 42 deletions
diff --git a/erts/emulator/beam/msg_instrs.tab b/erts/emulator/beam/msg_instrs.tab
index d6d4d2fb49..88d2ef9fa3 100644
--- a/erts/emulator/beam/msg_instrs.tab
+++ b/erts/emulator/beam/msg_instrs.tab
@@ -2,7 +2,7 @@
//
// %CopyrightBegin%
//
-// Copyright Ericsson AB 2017. All Rights Reserved.
+// Copyright Ericsson AB 2017-2018. 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.
@@ -45,23 +45,16 @@
i_recv_mark() {
/*
- * Save the current position in message buffer.
+ * Save the current end of message queue
*/
- c_p->msg.saved_last = c_p->msg.last;
+ ERTS_RECV_MARK_SAVE(c_p);
}
i_recv_set() {
/*
- * If c_p->msg.saved_last is non-zero, it points to the first
- * message that could possibly be matched out.
- *
- * If c_p->msg.saved_last is zero, it means that it was invalidated
- * because another receive was executed before this i_recv_set()
- * instruction was reached.
+ * If previously saved recv mark, set peek position to it
*/
- if (c_p->msg.saved_last) {
- c_p->msg.save = c_p->msg.saved_last;
- }
+ ERTS_RECV_MARK_SET(c_p);
SET_I($NEXT_INSTRUCTION);
goto loop_rec_top__;
//| -no_next
@@ -79,7 +72,6 @@ i_loop_rec(Dest) {
/* Entry point from recv_set */
loop_rec_top__:
- ;
/*
* We need to disable GC while matching messages
@@ -89,34 +81,59 @@ i_loop_rec(Dest) {
ASSERT(!(c_p->flags & F_DELAY_GC));
c_p->flags |= F_DELAY_GC;
- /* Entry point from loop_rec_end */
+ /* Entry point from loop_rec_end (and locally) */
loop_rec__:
+ if (FCALLS <= 0 && FCALLS <= neg_o_reds) {
+ $SET_CP_I_ABS(I);
+ c_p->flags &= ~F_DELAY_GC;
+ SWAPOUT;
+ c_p->arity = 0;
+ c_p->current = NULL;
+ goto do_schedule;
+ }
+
+ ASSERT(!ERTS_PROC_IS_EXITING(c_p));
+
PROCESS_MAIN_CHK_LOCKS(c_p);
msgp = PEEK_MESSAGE(c_p);
- if (!msgp) {
- erts_proc_lock(c_p, ERTS_PROC_LOCKS_MSG_RECEIVE);
- /* Make sure messages wont pass exit signals... */
- if (ERTS_PROC_PENDING_EXIT(c_p)) {
- erts_proc_unlock(c_p, ERTS_PROC_LOCKS_MSG_RECEIVE);
- SWAPOUT;
- c_p->flags &= ~F_DELAY_GC;
- c_p->arity = 0;
- goto do_schedule; /* Will be rescheduled for exit */
- }
- ERTS_MSGQ_MV_INQ2PRIVQ(c_p);
- msgp = PEEK_MESSAGE(c_p);
- if (msgp) {
- erts_proc_unlock(c_p, ERTS_PROC_LOCKS_MSG_RECEIVE);
- } else {
+ if (ERTS_UNLIKELY(msgp == NULL)) {
+ int get_out;
+ SWAPOUT;
+ FCALLS -= erts_proc_sig_receive_helper(c_p, FCALLS, neg_o_reds,
+ &msgp, &get_out);
+ SWAPIN;
+ if (ERTS_UNLIKELY(msgp == NULL)) {
+ if (get_out) {
+ if (get_out < 0) {
+ ASSERT(FCALLS <= 0 && FCALLS <= neg_o_reds);
+ goto loop_rec__; /* yield */
+ }
+ else {
+ ASSERT(ERTS_PROC_IS_EXITING(c_p));
+ goto do_schedule; /* exit */
+ }
+ }
+
+ /*
+ * If there are no more messages in queue
+ * (and we are not yielding or exiting)
+ * erts_proc_sig_receive_helper()
+ * returns with message queue lock locked...
+ */
c_p->flags &= ~F_DELAY_GC;
$SET_I_REL($Dest);
Goto(*I); /* Jump to a wait or wait_timeout instruction */
}
}
- if (is_non_value(ERL_MESSAGE_TERM(msgp))) {
+
+ ASSERT(msgp == PEEK_MESSAGE(c_p));
+ ASSERT(msgp && ERTS_SIG_IS_MSG(msgp));
+
+ if (ERTS_UNLIKELY(ERTS_SIG_IS_EXTERNAL_MSG(msgp))) {
+ FCALLS -= 10; /* FIXME: bump appropriate amount... */
SWAPOUT; /* erts_decode_dist_message() may write to heap... */
if (!erts_decode_dist_message(c_p, ERTS_PROC_LOCK_MAIN, msgp, 0)) {
/*
@@ -127,13 +144,16 @@ i_loop_rec(Dest) {
ASSERT(HTOP == c_p->htop && E == c_p->stop);
/* TODO: Add DTrace probe for this bad message situation? */
UNLINK_MESSAGE(c_p, msgp);
- c_p->msg.saved_last = 0; /* Better safe than sorry. */
msgp->next = NULL;
erts_cleanup_messages(msgp);
goto loop_rec__;
}
SWAPIN;
}
+
+ ASSERT(msgp == PEEK_MESSAGE(c_p));
+ ASSERT(ERTS_SIG_IS_INTERNAL_MSG(msgp));
+
r(0) = ERL_MESSAGE_TERM(msgp);
}
@@ -252,17 +272,8 @@ loop_rec_end(Dest) {
$SET_I_REL($Dest);
SAVE_MESSAGE(c_p);
- if (FCALLS > 0 || FCALLS > neg_o_reds) {
- FCALLS--;
- goto loop_rec__;
- }
-
- c_p->flags &= ~F_DELAY_GC;
- $SET_CP_I_ABS(I);
- SWAPOUT;
- c_p->arity = 0;
- c_p->current = NULL;
- goto do_schedule;
+ FCALLS--;
+ goto loop_rec__;
}
timeout_locked() {