File 4032-erts-Yield-when-adjusting-large-message-qu... of Package erlang

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File 4032-erts-Yield-when-adjusting-large-message-queues.patch of Package erlang (Revision b2172ea35270b4e41324f000c94154cb)

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From c13f7437adf4d02d05c94784180c553c3d776cff Mon Sep 17 00:00:00 2001
From: Rickard Green <rickard@erlang.org>
Date: Fri, 3 Dec 2021 20:11:50 +0100
Subject: [PATCH 2/2] [erts] Yield when adjusting large message queues

Yield when adjusting large process message queues due to
* copying terms from a literal area prior to removing the literal area.
* changing the 'message_queue_data' state from 'on_heap' to 'off_heap'.

The message queue adjustment work will now be interleaved with all other
types of work that processes have to do, even other message queue
adjustment work.
---
 erts/emulator/beam/atom.names                 |   1 +
 erts/emulator/beam/beam_bif_load.c            |  61 +-
 erts/emulator/beam/erl_alloc.types            |   1 +
 erts/emulator/beam/erl_message.h              |   1 +
 erts/emulator/beam/erl_proc_sig_queue.c       | 554 +++++++++++++++---
 erts/emulator/beam/erl_proc_sig_queue.h       |   7 +-
 erts/emulator/beam/erl_process.c              | 134 +++--
 erts/emulator/beam/erl_process.h              |   3 +-
 erts/emulator/beam/global.h                   |   1 +
 .../test/literal_area_collector_test.erl      |  51 +-
 erts/emulator/test/signal_SUITE.erl           | 314 +++++++++-
 .../ebin/erts_literal_area_collector.beam     | Bin 5616 -> 5932 bytes
 .../src/erts_literal_area_collector.erl       |  45 +-
 13 files changed, 994 insertions(+), 179 deletions(-)

diff --git a/erts/emulator/beam/atom.names b/erts/emulator/beam/atom.names
index 223603543f..f041227966 100644
--- a/erts/emulator/beam/atom.names
+++ b/erts/emulator/beam/atom.names
@@ -172,6 +172,7 @@ atom cflags
 atom CHANGE='CHANGE'
 atom characters_to_binary_int
 atom characters_to_list_int
+atom check_gc
 atom clear
 atom clock_service
 atom close
diff --git a/erts/emulator/beam/beam_bif_load.c b/erts/emulator/beam/beam_bif_load.c
index f910a4e8be..0e33dfa667 100644
--- a/erts/emulator/beam/beam_bif_load.c
+++ b/erts/emulator/beam/beam_bif_load.c
@@ -975,12 +975,39 @@ set_default_trace_pattern(Eterm module)
 }
 
 int
-erts_check_copy_literals_gc_need(Process *c_p, int *redsp,
-                                 char *literals, Uint lit_bsize)
+erts_check_copy_literals_gc_need_max_reds(Process *c_p)
 {
+    Uint64 words, reds;
+
     /*
-     * TODO: Implement yielding support!
+     * Calculate maximum amount of words that needs
+     * to be scanned...
      */
+    words = 1; /* fvalue */
+    words += c_p->hend - c_p->stop; /* stack */
+    words += c_p->htop - c_p->heap; /* new heap */
+    if (c_p->abandoned_heap)
+        words += c_p->heap_sz; /* abandoned heap */
+    words += c_p->old_htop - c_p->old_heap; /* old heap */
+    if (c_p->dictionary) {
+	Eterm* start = ERTS_PD_START(c_p->dictionary);
+	Eterm* end = start + ERTS_PD_SIZE(c_p->dictionary);
+
+        words += end - start; /* dictionary */
+    }
+    words += c_p->mbuf_sz; /* heap and message fragments */
+
+    /* Convert to reductions... */
+    reds = ((words - 1)/ERTS_CLA_SCAN_WORDS_PER_RED) + 1;
+    if (reds > CONTEXT_REDS)
+        return CONTEXT_REDS+1;
+    return (int) reds;
+}
+
+int
+erts_check_copy_literals_gc_need(Process *c_p, int *redsp,
+                                 char *literals, Uint lit_bsize)
+{
     ErlHeapFragment *hfrag;
     ErtsMessage *mfp;
     Uint64 scanned = 0;
@@ -1529,22 +1556,30 @@ erts_literal_area_collector_send_copy_request_3(BIF_ALIST_3)
 
     req_id = TUPLE3(&tmp_heap[0], BIF_ARG_2, BIF_ARG_3, BIF_ARG_1);
 
-    if (BIF_ARG_3 == am_false) {
+    switch (BIF_ARG_3) {
+
+    case am_init:
         /*
-         * Will handle signal queue and check if GC if needed. If
-         * GC is needed operation will be continued by a GC (below).
+         * Will handle signal queue and if possible check if GC if needed.
+         * If GC is needed or needs to be checked the operation will be
+         * restarted later in the 'check_gc' or 'need_gc' case below...
          */
         erts_proc_sig_send_cla_request(BIF_P, BIF_ARG_1, req_id);
-    }
-    else if (BIF_ARG_3 == am_true) {
+        break;
+
+    case am_check_gc:
+    case am_need_gc:
         /*
-         * Will perform a literal GC. Note that this assumes that
-         * signal queue already has been handled...
+         * Will check and/or perform a literal GC. Note that this assumes that
+         * signal queue already has been handled by 'init' case above...
          */
-        erts_schedule_cla_gc(BIF_P, BIF_ARG_1, req_id);
-    }
-    else
+        erts_schedule_cla_gc(BIF_P, BIF_ARG_1, req_id,
+                             BIF_ARG_3 == am_check_gc);
+        break;
+
+    default:
         BIF_ERROR(BIF_P, BADARG);
+    }
 
     BIF_RET(am_ok);
 }
diff --git a/erts/emulator/beam/erl_alloc.types b/erts/emulator/beam/erl_alloc.types
index 4aed5d9b34..24ba019075 100644
--- a/erts/emulator/beam/erl_alloc.types
+++ b/erts/emulator/beam/erl_alloc.types
@@ -274,6 +274,7 @@ 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	SIG_YIELD_DATA	SHORT_LIVED	PROCESSES	signal_yield_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
diff --git a/erts/emulator/beam/erl_message.h b/erts/emulator/beam/erl_message.h
index 87cd96f4cd..3a7aba5a68 100644
--- a/erts/emulator/beam/erl_message.h
+++ b/erts/emulator/beam/erl_message.h
@@ -284,6 +284,7 @@ typedef struct {
 typedef struct {
     ErtsSignal sig;
     ErtsMessage **prev_next;
+    signed char is_yield_mark;
     signed char pass;
     signed char set_save;
     signed char in_sigq;
diff --git a/erts/emulator/beam/erl_proc_sig_queue.c b/erts/emulator/beam/erl_proc_sig_queue.c
index bfddf9e48f..5b66c66c96 100644
--- a/erts/emulator/beam/erl_proc_sig_queue.c
+++ b/erts/emulator/beam/erl_proc_sig_queue.c
@@ -216,10 +216,25 @@ typedef struct {
 } ErtsProcSigRPC;
 
 typedef struct {
+    ErtsRecvMarker next;
+    ErtsRecvMarker last;
+} ErtsYieldAdjMsgQ;
+
+typedef struct {
+    ErtsYieldAdjMsgQ *yield;
     Eterm requester;
     Eterm request_id;
 } ErtsCLAData;
 
+typedef struct {
+    ErtsYieldAdjMsgQ *yield;
+} ErtsAdjOffHeapMsgQData;
+
+typedef struct {
+    ErtsMessage *first;
+    ErtsMessage **last;
+} ErtsSavedNMSignals;
+
 static void wake_handle_signals(Process *proc);
 
 static int handle_msg_tracing(Process *c_p,
@@ -243,12 +258,17 @@ static int
 handle_cla(Process *c_p,
            ErtsMessage *sig,
            ErtsMessage ***next_nm_sig,
-           int exiting);
+           int exiting,
+           int limit,
+           ErtsSavedNMSignals *saved_nm_sigs);
+
 static int
 handle_move_msgq_off_heap(Process *c_p,
 			  ErtsMessage *sig,
 			  ErtsMessage ***next_nm_sig,
-			  int exiting);
+			  int exiting,
+                          int limit,
+                          ErtsSavedNMSignals *saved_nm_sigs);
 static void
 send_cla_reply(Process *c_p, ErtsMessage *sig, Eterm to,
                Eterm req_id, Eterm result);
@@ -293,6 +313,76 @@ proc_sig_hdbg_check_queue(Process *c_p,
 #define ERTS_PROC_SIG_HDBG_PRIV_CHKQ(P, T, NMN)
 #endif
 
+static void
+save_delayed_nm_signal(ErtsSavedNMSignals *saved_sigs, ErtsMessage *sig)
+{
+    ErtsSignal *nm_sig = (ErtsSignal *) sig;
+    nm_sig->common.next = NULL;
+    nm_sig->common.specific.next = NULL;
+    if (!saved_sigs->first) {
+        ASSERT(!saved_sigs->last);
+        saved_sigs->first = sig;
+        saved_sigs->last = &saved_sigs->first;
+    }
+    else {
+        ErtsSignal *last;
+        ASSERT(saved_sigs->last);
+        last = (ErtsSignal *) *saved_sigs->last;
+        last->common.next = sig;
+        last->common.specific.next = &last->common.next;
+        saved_sigs->last = &last->common.next;
+    }
+}
+
+static erts_aint32_t
+restore_delayed_nm_signals(Process *c_p, ErtsSavedNMSignals *saved_sigs)
+{
+    erts_aint32_t state;
+    ErtsSignal *lsig;
+
+    ASSERT(saved_sigs->first && saved_sigs->last);
+
+    lsig = (ErtsSignal *) *saved_sigs->last;
+    if (!c_p->sig_qs.cont) {
+        ASSERT(!c_p->sig_qs.nmsigs.next);
+        ASSERT(!c_p->sig_qs.nmsigs.last);
+        if (saved_sigs->last == &saved_sigs->first) 
+            c_p->sig_qs.nmsigs.last = &c_p->sig_qs.cont;
+        else
+            c_p->sig_qs.nmsigs.last = saved_sigs->last;
+        c_p->sig_qs.cont_last = &lsig->common.next;
+    }
+    else {
+        lsig->common.next = c_p->sig_qs.cont;
+        if (c_p->sig_qs.nmsigs.next) {
+            ASSERT(c_p->sig_qs.nmsigs.last);
+            if (c_p->sig_qs.nmsigs.next == &c_p->sig_qs.cont)
+                lsig->common.specific.next = &lsig->common.next;
+            else
+                lsig->common.specific.next = c_p->sig_qs.nmsigs.next;
+            if (c_p->sig_qs.nmsigs.last == &c_p->sig_qs.cont)
+                c_p->sig_qs.nmsigs.last = &lsig->common.next;
+        }
+        else {
+            ASSERT(!c_p->sig_qs.nmsigs.last);
+            if (saved_sigs->last == &saved_sigs->first) 
+                c_p->sig_qs.nmsigs.last = &c_p->sig_qs.cont;
+            else
+                c_p->sig_qs.nmsigs.last = saved_sigs->last;
+            if (c_p->sig_qs.cont_last == &c_p->sig_qs.cont)
+                c_p->sig_qs.cont_last = &lsig->common.next;
+        }
+    }
+    
+    c_p->sig_qs.cont = saved_sigs->first;
+    c_p->sig_qs.nmsigs.next = &c_p->sig_qs.cont;
+
+    state = erts_atomic32_read_bor_nob(&c_p->state,
+                                       ERTS_PSFLG_SIG_Q);
+    state |= ERTS_PSFLG_SIG_Q;
+    return state;
+}
+
 typedef struct {
     ErtsSignalCommon common;
     Eterm ref;
@@ -389,6 +479,18 @@ get_cla_data(ErtsMessage *sig)
                                      + sig->hfrag.used_size);
 }
 
+static ERTS_INLINE ErtsAdjOffHeapMsgQData *
+get_move_msgq_off_heap_data(ErtsMessage *sig)
+{
+    ASSERT(ERTS_SIG_IS_NON_MSG(sig));
+    ASSERT(ERTS_PROC_SIG_OP(((ErtsSignal *) sig)->common.tag)
+           == ERTS_SIG_Q_OP_ADJ_MSGQ);
+    ASSERT(ERTS_PROC_SIG_TYPE(((ErtsSignal *) sig)->common.tag)
+           == ERTS_SIG_Q_TYPE_OFF_HEAP);
+    return (ErtsAdjOffHeapMsgQData *) (char *) (&sig->hfrag.mem[0]
+                                                + sig->hfrag.used_size);
+}
+
 static ERTS_INLINE void
 destroy_trace_info(ErtsSigTraceInfo *ti)
 {
@@ -598,7 +700,7 @@ enqueue_signals(Process *rp, ErtsMessage *first,
 
     this = dest_queue->last;
 
-    if ( ! is_to_buffer ){
+    if (!is_to_buffer) {
         ERTS_HDBG_CHECK_SIGNAL_IN_QUEUE(rp);
     }
 
@@ -664,7 +766,9 @@ enqueue_signals(Process *rp, ErtsMessage *first,
 
     dest_queue->len += num_msgs;
 
-    ERTS_HDBG_CHECK_SIGNAL_IN_QUEUE(rp);
+    if (!is_to_buffer) {
+        ERTS_HDBG_CHECK_SIGNAL_IN_QUEUE(rp);
+    }
 
     return state;
 }
@@ -1468,22 +1572,17 @@ erts_proc_sig_cleanup_non_msg_signal(ErtsMessage *sig)
     Eterm tag = ((ErtsSignal *) sig)->common.tag;
     
     /*
-     * Heap alias message, heap frag alias message and
-     * adjust message queue signals are the only non-message
-     * signals, which are allocated as messages, which do not
-     * use a combined message / heap fragment.
+     * Heap alias message and heap frag alias message are
+     * the only non-message signals, which are allocated as
+     * messages, which do not use a combined message / heap
+     * fragment.
      */
-    if (ERTS_SIG_IS_HEAP_ALIAS_MSG_TAG(tag)
-	|| tag == ERTS_PROC_SIG_MAKE_TAG(ERTS_SIG_Q_OP_ADJ_MSGQ,
-					 ERTS_SIG_Q_TYPE_OFF_HEAP,
-					 0)) {
+    if (ERTS_SIG_IS_HEAP_ALIAS_MSG_TAG(tag)) {
         sig->data.heap_frag = NULL;
         return;
     }
 
-    
-
-    if(ERTS_SIG_IS_HEAP_FRAG_ALIAS_MSG_TAG(tag)) {
+    if (ERTS_SIG_IS_HEAP_FRAG_ALIAS_MSG_TAG(tag)) {
         /* Retrieve pointer to heap fragment (may not be NULL). */
         void *attached;
         (void) get_alias_msg_data(sig, NULL, NULL, NULL, &attached);
@@ -1494,10 +1593,45 @@ erts_proc_sig_cleanup_non_msg_signal(ErtsMessage *sig)
         /*
          * Using a combined heap fragment...
          */
-        ErtsDistExternal *edep = get_external_non_msg_signal(sig);
-        if (edep)
-            erts_free_dist_ext_copy(edep);
-    
+        switch (ERTS_PROC_SIG_OP(tag)) {
+
+        case ERTS_SIG_Q_OP_ADJ_MSGQ: {
+            /* We need to deallocate yield markers if such has been used... */
+            ErtsYieldAdjMsgQ *yp;
+            switch (ERTS_PROC_SIG_TYPE(tag)) {
+            case ERTS_SIG_Q_TYPE_CLA: {
+                ErtsCLAData *cla = get_cla_data(sig);
+                yp = cla->yield;
+                cla->yield = NULL;
+                break;
+            }
+            case ERTS_SIG_Q_TYPE_OFF_HEAP: {
+                ErtsAdjOffHeapMsgQData *ohdp = get_move_msgq_off_heap_data(sig);
+                yp = ohdp->yield;
+                ohdp->yield = NULL;
+                break;
+            }
+            default:
+                ERTS_INTERNAL_ERROR("Invalid adjust-message-queue signal type");
+                yp = NULL;
+                break;
+            }
+            if (yp) {
+                ASSERT(!yp->next.in_msgq && !yp->next.in_sigq);
+                ASSERT(!yp->last.in_msgq && !yp->last.in_sigq);
+                erts_free(ERTS_ALC_T_SIG_YIELD_DATA, yp);
+            }
+            break;
+        }
+
+        default: {
+            ErtsDistExternal *edep = get_external_non_msg_signal(sig);
+            if (edep)
+                erts_free_dist_ext_copy(edep);
+            break;
+        }
+        }
+
         sig->data.attached = ERTS_MSG_COMBINED_HFRAG;
         hfrag = sig->hfrag.next;
         erts_cleanup_offheap(&sig->hfrag.off_heap);
@@ -2717,6 +2851,7 @@ erts_proc_sig_send_cla_request(Process *c_p, Eterm to, Eterm req_id)
     cla = (ErtsCLAData *) (char *) hp;
     hfrag->used_size = hp - start_hp;
 
+    cla->yield = NULL;
     cla->requester = c_p->common.id;
     cla->request_id = req_id_cpy;
 
@@ -2738,8 +2873,20 @@ erts_proc_sig_send_cla_request(Process *c_p, Eterm to, Eterm req_id)
 void
 erts_proc_sig_send_move_msgq_off_heap(Eterm to)
 {
-    ErtsMessage *sig = erts_alloc_message(0, NULL);
+    ErtsMessage *sig;
+    Eterm *hp;
+    Uint hsz;
+    ErtsAdjOffHeapMsgQData *ohdp;
     ASSERT(is_internal_pid(to));
+
+    hsz = sizeof(ErtsAdjOffHeapMsgQData)/sizeof(Uint);
+    sig = erts_alloc_message(hsz, &hp);
+
+    ohdp = (ErtsAdjOffHeapMsgQData *) (char *) hp;
+    ohdp->yield = NULL;
+
+    sig->hfrag.used_size = 0;
+
     ERL_MESSAGE_TERM(sig) = ERTS_PROC_SIG_MAKE_TAG(ERTS_SIG_Q_OP_ADJ_MSGQ,
                                                    ERTS_SIG_Q_TYPE_OFF_HEAP,
                                                    0);
@@ -3019,7 +3166,7 @@ remove_iq_sig(Process *c_p, ErtsMessage *sig, ErtsMessage **next_sig)
 
 static ERTS_INLINE void
 remove_mq_sig(Process *c_p, ErtsMessage *sig,
-           ErtsMessage **next_sig, ErtsMessage ***next_nm_sig)
+              ErtsMessage **next_sig, ErtsMessage ***next_nm_sig)
 {
     /*
      * Remove signal from (middle) signal queue.
@@ -3247,6 +3394,8 @@ recv_marker_deallocate(Process *c_p, ErtsRecvMarker *markp)
     ErtsRecvMarkerBlock *blkp = c_p->sig_qs.recv_mrk_blk;
     int ix, nix;
 
+    ASSERT(!markp->is_yield_mark);
+    
     ASSERT(blkp);
     ERTS_HDBG_CHK_RECV_MRKS(c_p);
 
@@ -3297,6 +3446,7 @@ recv_marker_dequeue(Process *c_p, ErtsRecvMarker *markp)
 {
     ErtsMessage *sigp;
 
+    ASSERT(!markp->is_yield_mark);
     ASSERT(markp->proc == c_p);
 
     if (markp->in_sigq <= 0) {
@@ -3362,6 +3512,7 @@ recv_marker_alloc_block(Process *c_p, ErtsRecvMarkerBlock **blkpp,
     /* Allocate marker for 'uniqp' in index zero... */    
     *ixp = 0;
     blkp->ref[0] = recv_marker_uniq(c_p, uniqp);
+    blkp->marker[0].is_yield_mark = 0;
     markp = &blkp->marker[0];
     markp->next_ix = markp->prev_ix = 0;
     blkp->used_ix = 0;
@@ -3377,6 +3528,7 @@ recv_marker_alloc_block(Process *c_p, ErtsRecvMarkerBlock **blkpp,
     blkp->free_ix = 1;
     for (ix = 1; ix < ERTS_RECV_MARKER_BLOCK_SIZE; ix++) {
 	blkp->ref[ix] = am_free;
+        blkp->marker[ix].is_yield_mark = 0;
 	if (ix == ERTS_RECV_MARKER_BLOCK_SIZE - 1)
 	    blkp->marker[ix].next_ix = -1; /* End of list */
 	else
@@ -3644,20 +3796,29 @@ erts_msgq_recv_marker_create_insert_set_save(Process *c_p, Eterm id)
 }
 
 void
-erts_msgq_remove_leading_recv_markers(Process *c_p)
+erts_msgq_remove_leading_recv_markers_set_save_first(Process *c_p)
 {
+    ErtsMessage **save;
     /*
      * Receive markers in the front of the queue does not
-     * add any value, so we just remove them...
+     * add any value, so we just remove them. We need to
+     * keep and pass yield markers though...
      */
     ASSERT(c_p->sig_qs.first
 	   && ERTS_SIG_IS_RECV_MARKER(c_p->sig_qs.first));
     ERTS_HDBG_CHECK_SIGNAL_PRIV_QUEUE(c_p, 0);
+    save = &c_p->sig_qs.first;
     do {
-	ErtsRecvMarker *markp = (ErtsRecvMarker *) c_p->sig_qs.first;
-	recv_marker_dequeue(c_p, markp);
-    } while (c_p->sig_qs.first
-	     && ERTS_SIG_IS_RECV_MARKER(c_p->sig_qs.first));
+	ErtsRecvMarker *markp = (ErtsRecvMarker *) *save;
+        if (markp->is_yield_mark)
+            save = &markp->sig.common.next;
+        else
+            recv_marker_dequeue(c_p, markp);
+    } while (*save && ERTS_SIG_IS_RECV_MARKER(*save));
+
+    c_p->sig_qs.save = save;
+
+    ASSERT(!*save || ERTS_SIG_IS_MSG(*save));
     ERTS_HDBG_CHECK_SIGNAL_PRIV_QUEUE(c_p, 0);
 }
 
@@ -3669,7 +3830,8 @@ erts_msgq_pass_recv_markers(Process *c_p, ErtsMessage **markpp)
     ASSERT(ERTS_SIG_IS_RECV_MARKER(sigp));
     do {
 	ErtsRecvMarker *markp = (ErtsRecvMarker *) sigp;
-	if (++markp->pass > ERTS_RECV_MARKER_PASS_MAX) {
+	if (!markp->is_yield_mark
+            && ++markp->pass > ERTS_RECV_MARKER_PASS_MAX) {
 	    recv_marker_dequeue(c_p, markp);
 	    sigp = *sigpp;
 	}
@@ -5235,7 +5397,8 @@ erts_proc_sig_handle_incoming(Process *c_p, erts_aint32_t *statep,
     int yield, cnt, limit, abs_lim, msg_tracing, save_in_msgq;
     ErtsMessage *sig, ***next_nm_sig;
     ErtsSigRecvTracing tracing;
-
+    ErtsSavedNMSignals delayed_nm_signals = {0};
+    
     ASSERT(!(c_p->sig_qs.flags & (FS_WAIT_HANDLE_SIGS|FS_HANDLING_SIGS)));
 
     ERTS_HDBG_CHECK_SIGNAL_PRIV_QUEUE(c_p, 0);
@@ -5759,21 +5922,43 @@ erts_proc_sig_handle_incoming(Process *c_p, erts_aint32_t *statep,
             ERTS_PROC_SIG_HDBG_PRIV_CHKQ(c_p, &tracing, next_nm_sig);
             break;
 
-        case ERTS_SIG_Q_OP_ADJ_MSGQ:
+        case ERTS_SIG_Q_OP_ADJ_MSGQ: {
+            int adj_limit, adj_cnt, min_adj_limit;
+            /*
+             * This may require a substantial amount of work and we
+             * want to get it over and done with in a reasonable
+             * amount of time, so we bump up the limit for it a bit...
+             */
+            min_adj_limit = ERTS_SIG_REDS_CNT_FACTOR*CONTEXT_REDS/6;
+            if (sig->next)
+                adj_limit = min_adj_limit;
+            else {
+                adj_limit = limit - cnt;
+                if (adj_limit < min_adj_limit)
+                    adj_limit = min_adj_limit;
+            }
             ERTS_PROC_SIG_HDBG_PRIV_CHKQ(c_p, &tracing, next_nm_sig);
 	    switch (ERTS_PROC_SIG_TYPE(tag)) {
 	    case ERTS_SIG_Q_TYPE_CLA:
-		cnt += handle_cla(c_p, sig, next_nm_sig, 0);
+		adj_cnt = handle_cla(c_p, sig, next_nm_sig, 0, adj_limit,
+                                     &delayed_nm_signals);
 		break;
 	    case ERTS_SIG_Q_TYPE_OFF_HEAP:
-		cnt += handle_move_msgq_off_heap(c_p, sig, next_nm_sig, 0);
+		adj_cnt = handle_move_msgq_off_heap(c_p, sig, next_nm_sig,
+                                                    0, adj_limit,
+                                                    &delayed_nm_signals);
 		break;
 	    default:
-		ERTS_INTERNAL_ERROR("Invalid 'adjust-message-queue' signal type");
+		ERTS_INTERNAL_ERROR("Invalid adjust-message-queue signal type");
 		break;
 	    }
+            cnt += adj_cnt;
+            limit += adj_cnt;
+            if (limit > abs_lim)
+                abs_lim = limit;
             ERTS_PROC_SIG_HDBG_PRIV_CHKQ(c_p, &tracing, next_nm_sig);
             break;
+        }
 
 	case ERTS_SIG_Q_OP_FLUSH:
             ERTS_PROC_SIG_HDBG_PRIV_CHKQ(c_p, &tracing, next_nm_sig);
@@ -5818,6 +6003,7 @@ erts_proc_sig_handle_incoming(Process *c_p, erts_aint32_t *statep,
         case ERTS_SIG_Q_OP_RECV_MARK: {
             ErtsRecvMarker *markp = (ErtsRecvMarker *) sig;
             ASSERT(markp->in_sigq);
+            ASSERT(!markp->is_yield_mark);
 
             if (markp->in_sigq < 0) {
                 /* Marked for removal... */
@@ -6000,10 +6186,25 @@ stop: {
 	     * We know we do not have any outstanding signals
 	     * from ourselves...
 	     */
-	    (void) erts_atomic32_read_band_nob(&c_p->state,
-					       ~ERTS_PSFLG_MAYBE_SELF_SIGS);
+	    state = erts_atomic32_read_band_nob(&c_p->state,
+                                                ~ERTS_PSFLG_MAYBE_SELF_SIGS);
 	    state &= ~ERTS_PSFLG_MAYBE_SELF_SIGS;
 	}
+
+        if (delayed_nm_signals.first) {
+            /*
+             * We do this after clearing ERTS_PSFLG_MAYBE_SELF_SIGS
+             * since there currently are no signals that can be delayed
+             * that should be counted as originating from the process
+             * itself. If such signals appear in the future this has to
+             * be accounted for...
+             *
+             * The adjust message queue data "signal" does originate from
+             * the process itself, but it is not conseptually a signal.
+             */
+            state = restore_delayed_nm_signals(c_p, &delayed_nm_signals);
+        }
+
 	*statep = state;
 
         /* Ensure that 'save' doesn't point to a receive marker... */
@@ -6015,7 +6216,7 @@ stop: {
 
         ERTS_HDBG_CHECK_SIGNAL_PRIV_QUEUE(c_p, 0);
 
-        *redsp = cnt/4 + 1;
+        *redsp = cnt/ERTS_SIG_REDS_CNT_FACTOR + 1;
 
         if (yield) {
             int vreds = max_reds - *redsp;
@@ -6277,13 +6478,14 @@ erts_proc_sig_handle_exit(Process *c_p, Sint *redsp,
         case ERTS_SIG_Q_OP_ADJ_MSGQ:
 	    switch (ERTS_PROC_SIG_TYPE(tag)) {
 	    case ERTS_SIG_Q_TYPE_CLA:
-		handle_cla(c_p, sig, next_nm_sig, !0);
+		handle_cla(c_p, sig, next_nm_sig, !0, limit, NULL);
 		break;
 	    case ERTS_SIG_Q_TYPE_OFF_HEAP:
-		handle_move_msgq_off_heap(c_p, sig, next_nm_sig, !0);
+		handle_move_msgq_off_heap(c_p, sig, next_nm_sig, !0,
+                                          limit, NULL);
 		break;
 	    default:
-		ERTS_INTERNAL_ERROR("Invalid 'adjust-message-queue' signal type");
+		ERTS_INTERNAL_ERROR("Invalid adjust-message-queue signal type");
 		break;
 	    }
             break;
@@ -6300,6 +6502,7 @@ erts_proc_sig_handle_exit(Process *c_p, Sint *redsp,
 
         case ERTS_SIG_Q_OP_RECV_MARK: {
             ErtsRecvMarker *markp = (ErtsRecvMarker *) sig;
+            ASSERT(!markp->is_yield_mark);
             markp->in_msgq = markp->in_sigq = markp->set_save = 0;
             recv_marker_deallocate(c_p, markp);
             break;
@@ -6477,11 +6680,6 @@ erts_proc_sig_signal_size(ErtsSignal *sig)
         break;
 
     case ERTS_SIG_Q_OP_ADJ_MSGQ:
-	if (type == ERTS_SIG_Q_TYPE_OFF_HEAP) {
-	    size = sizeof(ErtsMessageRef);
-	    break;
-	}
-	/* Fall through... */
     case ERTS_SIG_Q_OP_SYNC_SUSPEND:
     case ERTS_SIG_Q_OP_PERSISTENT_MON_MSG:
     case ERTS_SIG_Q_OP_IS_ALIVE:
@@ -6717,7 +6915,6 @@ erts_proc_sig_receive_helper(Process *c_p,
         if (left_reds <= 0)
             break; /* yield */
 
-        ASSERT(!c_p->sig_qs.cont);
         /* Go fetch again... */
     }
     
@@ -6730,6 +6927,127 @@ erts_proc_sig_receive_helper(Process *c_p,
     return consumed_reds;
 }
 
+static void
+init_yield_marker(Process *c_p, ErtsRecvMarker *mrkp)
+{
+    mrkp->prev_next = NULL;
+    mrkp->is_yield_mark = (char) !0;
+    mrkp->pass = (char) 100;
+    mrkp->set_save = (char) 0;
+    mrkp->in_sigq = (char) 0;
+    mrkp->in_msgq = (char) 0;
+    mrkp->prev_ix = (char) -100;
+    mrkp->next_ix = (char) -100;
+#ifdef DEBUG
+    mrkp->used = (char) !0;
+    mrkp->proc = c_p;
+#endif
+    mrkp->sig.common.next = NULL;
+    mrkp->sig.common.specific.attachment = NULL;
+    mrkp->sig.common.tag = ERTS_RECV_MARKER_TAG;
+}
+
+static void
+remove_yield_marker(Process *c_p, ErtsRecvMarker *mrkp)
+{
+    ASSERT(mrkp);
+    ASSERT(mrkp->is_yield_mark);
+    ASSERT(mrkp->in_msgq);
+    remove_iq_sig(c_p, (ErtsMessage *) mrkp, mrkp->prev_next);
+    mrkp->in_msgq = 0;
+    mrkp->in_sigq = 0;
+    mrkp->prev_next = NULL;
+    mrkp->sig.common.next = NULL;
+}
+
+static ErtsYieldAdjMsgQ *
+create_yield_adj_msgq_data(Process *c_p)
+{
+    ErtsYieldAdjMsgQ *yp = erts_alloc(ERTS_ALC_T_SIG_YIELD_DATA,
+                                      sizeof(ErtsYieldAdjMsgQ));
+    init_yield_marker(c_p, &yp->next);
+    init_yield_marker(c_p, &yp->last);
+    return yp;
+}
+
+static ERTS_INLINE void
+insert_adj_msgq_yield_markers(Process *c_p,
+                              ErtsYieldAdjMsgQ *yp,
+                              ErtsMessage **nextpp,
+                              ErtsMessage ***next_nm_sig,
+                              ErtsSavedNMSignals *saved_sigs)
+{
+    ErtsMessage *sig, *nextp;
+
+    ASSERT(yp);
+    ASSERT(nextpp);
+    ASSERT(next_nm_sig && *next_nm_sig && **next_nm_sig);
+    ASSERT(!yp->next.in_msgq);
+
+    sig = **next_nm_sig;
+
+    ASSERT(ERTS_PROC_SIG_OP(ERL_MESSAGE_TERM(sig))
+           == ERTS_SIG_Q_OP_ADJ_MSGQ);
+
+    /*
+     * Insert 'next' yield marker. This is in the inner queue or
+     * in the beginning of the middle queue where we've already
+     * begun using 'prev_next' pointers for receive markers,
+     * so if a receive marker follow, we need to update it.
+     */
+    yp->next.in_msgq = !0;
+    yp->next.in_sigq = !0;
+    yp->next.prev_next = nextpp;
+    yp->next.sig.common.next = nextp = *nextpp;
+    *nextpp = (ErtsMessage *) &yp->next;
+
+    ERTS_SIG_DBG_RECV_MARK_SET_HANDLED(&yp->next);
+
+    if (nextp && ERTS_SIG_IS_RECV_MARKER(nextp)) {
+        ErtsRecvMarker *next_mrkp = (ErtsRecvMarker *) nextp;
+        next_mrkp->prev_next = &yp->next.sig.common.next;
+    }
+
+    if (yp->last.in_msgq) {
+        remove_nm_sig(c_p, sig, next_nm_sig);
+    }
+    else {
+        /*
+         * Replace adj-msgq signal with 'last' yield marker.
+         *
+         * This is in the middle queue after the point where
+         * we've begun using 'prev_next' pointers for receive
+         * markers, so if a receive marker follow, we do not
+         * need to adjust its 'prev_next'.
+         */
+        ErtsMessage **next_sig = *next_nm_sig;
+        yp->last.in_msgq = (char) !0;
+        yp->last.in_sigq = (char) !0;
+        yp->last.prev_next = next_sig;
+        *next_nm_sig = ((ErtsSignal *) sig)->common.specific.next;
+        *next_sig = (ErtsMessage *) &yp->last;
+        remove_mq_sig(c_p, sig, &yp->last.sig.common.next, next_nm_sig);
+
+        ERTS_SIG_DBG_RECV_MARK_SET_HANDLED(&yp->last);
+    }
+
+    save_delayed_nm_signal(saved_sigs, sig);
+}
+
+static ERTS_INLINE void
+destroy_adj_msgq_yield_markers(Process *c_p, ErtsYieldAdjMsgQ **ypp)
+{
+    ErtsYieldAdjMsgQ *yp = *ypp;
+    if (yp) {
+        if (yp->next.in_msgq)
+            remove_yield_marker(c_p, &yp->next);
+        if (yp->last.in_msgq)
+            remove_yield_marker(c_p, &yp->last);
+        erts_free(ERTS_ALC_T_SIG_YIELD_DATA, yp);
+        *ypp = NULL;
+    }
+}
+
 static Uint
 area_literal_size(Eterm* start, Eterm* end, char* lit_start, Uint lit_size)
 {
@@ -6851,17 +7169,16 @@ static int
 handle_cla(Process *c_p,
            ErtsMessage *sig,
            ErtsMessage ***next_nm_sig,
-           int exiting)
+           int exiting,
+           int limit,
+           ErtsSavedNMSignals *saved_nm_sigs)
 {
-    /*
-     * TODO: Implement yielding support!
-     */
     ErtsCLAData *cla;
-    ErtsMessage *msg;
+    ErtsMessage *msg, *endp;
     ErtsLiteralArea *la;
     char *literals;
     Uint lit_bsize;
-    int nmsgs, reds;
+    int nmsgs, reds, stretch_yield_limit = 0;
     Eterm result = am_ok;
     Uint64 cnt = 0;
 
@@ -6882,6 +7199,30 @@ handle_cla(Process *c_p,
      * can therefore occur behind this signal.
      */
 
+    msg = c_p->sig_qs.first;
+    if (!msg)
+        msg = c_p->sig_qs.cont;
+
+    if (!cla->yield) {
+        endp = sig;
+    }
+    else {
+        if (!cla->yield->next.in_msgq) {
+            /* All messages already handled... */
+            ASSERT(!cla->yield->last.in_msgq);
+            stretch_yield_limit = !0;
+            endp = msg = sig;
+        }
+        else {
+            ASSERT(!!cla->yield->last.in_msgq);
+            msg = cla->yield->next.sig.common.next;
+            endp = (ErtsMessage *) &cla->yield->last;
+            remove_yield_marker(c_p, &cla->yield->next);
+        }
+    }
+
+    ASSERT(!cla->yield || !cla->yield->next.in_msgq);
+    
     la = ERTS_COPY_LITERAL_AREA();
     if (!la) {
         ASSERT(0);
@@ -6894,12 +7235,8 @@ handle_cla(Process *c_p,
     literals = (char *) &la->start[0];
     lit_bsize = (char *) la->end - literals;
 
-    msg = c_p->sig_qs.first;
-    if (!msg)
-        msg = c_p->sig_qs.cont;
-
     nmsgs = 0;
-    while (msg != sig) {
+    while (msg != endp) {
         ASSERT(!!msg);
         nmsgs++;
         if (nmsgs >= ERTS_PROC_SIG_ADJ_MSGQ_MSGS_FACTOR) {
@@ -6994,6 +7331,18 @@ handle_cla(Process *c_p,
             }
         }
 
+        if (cnt > limit) { /* yield... */
+            ErtsMessage **nextpp = !msg->next ? &c_p->sig_qs.cont : &msg->next;
+            ASSERT(*nextpp);
+            if (*nextpp == endp)
+                break; /* we're at the end; no point yielding here... */
+            if (!cla->yield)
+                cla->yield = create_yield_adj_msgq_data(c_p);
+            insert_adj_msgq_yield_markers(c_p, cla->yield, nextpp,
+                                          next_nm_sig, saved_nm_sigs);
+            return cnt;
+        }
+
         msg = msg->next;
         if (!msg)
             msg = c_p->sig_qs.cont;
@@ -7001,18 +7350,36 @@ handle_cla(Process *c_p,
 
     remove_nm_sig(c_p, sig, next_nm_sig);
 
-    reds = 0;
-    if (erts_check_copy_literals_gc_need(c_p, &reds, literals, lit_bsize))
-        result = am_need_gc;
-
-    cnt += reds * ERTS_SIG_REDS_CNT_FACTOR;
+    reds = erts_check_copy_literals_gc_need_max_reds(c_p);
+    cnt++;
+    if (reds > CONTEXT_REDS)
+        result = am_check_gc;
+    else if (stretch_yield_limit
+             || cnt + reds*ERTS_SIG_REDS_CNT_FACTOR <= limit) {
+        reds = 0;
+        if (erts_check_copy_literals_gc_need(c_p, &reds, literals, lit_bsize))
+            result = am_need_gc;
+        cnt += reds * ERTS_SIG_REDS_CNT_FACTOR;
+    }
+    else {
+        /* yield... */
+        if (!cla->yield)
+            cla->yield = create_yield_adj_msgq_data(c_p);
+        else if (!!cla->yield->last.in_msgq)
+            remove_yield_marker(c_p, &cla->yield->last);
+        ASSERT(!cla->yield->next.in_msgq);
+        save_delayed_nm_signal(saved_nm_sigs, sig);
+        return cnt;
+    }
 
 done:
 
+    destroy_adj_msgq_yield_markers(c_p, &cla->yield);
+
     send_cla_reply(c_p, sig, cla->requester, cla->request_id, result);
 
-    if (cnt > CONTEXT_REDS)
-        return CONTEXT_REDS;
+    if (cnt > CONTEXT_REDS*ERTS_SIG_REDS_CNT_FACTOR)
+        return CONTEXT_REDS*ERTS_SIG_REDS_CNT_FACTOR;
     return cnt;
 }
 
@@ -7020,12 +7387,12 @@ static int
 handle_move_msgq_off_heap(Process *c_p,
 			  ErtsMessage *sig,
 			  ErtsMessage ***next_nm_sig,
-			  int exiting)
+			  int exiting,
+                          int limit,
+                          ErtsSavedNMSignals *saved_nm_sigs)
 {
-    /*
-     * TODO: Implement yielding support!
-     */
-    ErtsMessage *msg;
+    ErtsAdjOffHeapMsgQData *ohdp;
+    ErtsMessage *msg, *endp;
     int nmsgs;
     Uint64 cnt = 0;
 
@@ -7045,6 +7412,8 @@ handle_move_msgq_off_heap(Process *c_p,
 
     cnt++;
 
+    ohdp = get_move_msgq_off_heap_data(sig);
+
     if (exiting) {
 	/* signal already removed from queue... */
 	goto cleanup;
@@ -7065,8 +7434,21 @@ handle_move_msgq_off_heap(Process *c_p,
     if (!msg)
         msg = c_p->sig_qs.cont;
 
+    if (!ohdp->yield) {
+        endp = sig;
+    }
+    else {
+        ASSERT(!!ohdp->yield->next.in_msgq);
+        ASSERT(!!ohdp->yield->last.in_msgq);
+        msg = ohdp->yield->next.sig.common.next;
+        endp = (ErtsMessage *) &ohdp->yield->last;
+        remove_yield_marker(c_p, &ohdp->yield->next);
+    }
+
+    ASSERT(!ohdp->yield || !ohdp->yield->next.in_msgq);
+    
     nmsgs = 0;
-    while (msg != sig) {
+    while (msg != endp) {
         ASSERT(!!msg);
         nmsgs++;
         if (nmsgs >= ERTS_PROC_SIG_ADJ_MSGQ_MSGS_FACTOR) {
@@ -7143,6 +7525,18 @@ handle_move_msgq_off_heap(Process *c_p,
 	    cnt += h_sz/ERTS_PROC_SIG_ADJ_MSGQ_COPY_FACTOR;
 	}
 
+        if (cnt > limit) { /* yield... */
+            ErtsMessage **nextpp = !msg->next ? &c_p->sig_qs.cont : &msg->next;
+            ASSERT(*nextpp);
+            if (*nextpp == endp)
+                break; /* we're at the end; no point yielding... */
+            if (!ohdp->yield)
+                ohdp->yield = create_yield_adj_msgq_data(c_p);
+            insert_adj_msgq_yield_markers(c_p, ohdp->yield, nextpp,
+                                          next_nm_sig, saved_nm_sigs);
+            return cnt;
+        }
+
         msg = msg->next;
         if (!msg)
             msg = c_p->sig_qs.cont;
@@ -7154,13 +7548,15 @@ done:
 
 cleanup:
 
+    destroy_adj_msgq_yield_markers(c_p, &ohdp->yield);
     sig->next = NULL;
+    sig->data.attached = ERTS_MSG_COMBINED_HFRAG;
     erts_cleanup_messages(sig);
 
     c_p->sig_qs.flags &= ~FS_OFF_HEAP_MSGQ_CHNG;
 
-    if (cnt > CONTEXT_REDS)
-        return CONTEXT_REDS;
+    if (cnt > CONTEXT_REDS*ERTS_SIG_REDS_CNT_FACTOR)
+        return CONTEXT_REDS*ERTS_SIG_REDS_CNT_FACTOR;
     return cnt;
 }
 
@@ -7601,9 +7997,13 @@ erts_proc_sig_cleanup_queues(Process *c_p)
 	while (sig) {
 	    ErtsMessage *free_sig = sig;
 	    sig = sig->next;
-	    if (ERTS_SIG_IS_RECV_MARKER(free_sig))
-		recv_marker_deallocate(c_p, (ErtsRecvMarker *) free_sig);
+	    if (ERTS_SIG_IS_RECV_MARKER(free_sig)) {
+                ErtsRecvMarker *recv_mark = (ErtsRecvMarker *) free_sig;
+                ASSERT(!recv_mark->is_yield_mark);
+                recv_marker_deallocate(c_p, recv_mark);
+            }
 	    else {
+                ASSERT(ERTS_SIG_IS_MSG(free_sig));
 		free_sig->next = NULL;
 		erts_cleanup_messages(free_sig);
 	    }
@@ -7801,9 +8201,6 @@ erts_proc_sig_debug_foreach_sig(Process *c_p,
                     break;
 
                 case ERTS_SIG_Q_OP_ADJ_MSGQ:
-		    if (type == ERTS_SIG_Q_TYPE_OFF_HEAP)
-			break;
-		    /* Fall through... */
                 case ERTS_SIG_Q_OP_PERSISTENT_MON_MSG:
                     debug_foreach_sig_heap_frags(&sig->hfrag, oh_func, arg);
                     break;
@@ -8146,7 +8543,10 @@ proc_sig_hdbg_check_queue(Process *proc,
 
     if (sig_psflg != ERTS_PSFLG_FREE) {
         erts_aint32_t state = erts_atomic32_read_nob(&proc->state);
-        ERTS_ASSERT(nm_sigs ? !!(state & sig_psflg) : !(state & sig_psflg));
+        ERTS_ASSERT(nm_sigs
+                    ? !!(state & sig_psflg)
+                    : (!(state & sig_psflg)
+                       || !!erts_atomic_read_nob(&proc->sig_inq_buffers)));
     }
 
     return msg_len;
diff --git a/erts/emulator/beam/erl_proc_sig_queue.h b/erts/emulator/beam/erl_proc_sig_queue.h
index deb1b802e1..8faa79507f 100644
--- a/erts/emulator/beam/erl_proc_sig_queue.h
+++ b/erts/emulator/beam/erl_proc_sig_queue.h
@@ -1736,7 +1736,7 @@ Eterm erts_msgq_recv_marker_create_insert(Process *c_p, Eterm id);
 void erts_msgq_recv_marker_create_insert_set_save(Process *c_p, Eterm id);
 ErtsMessage **erts_msgq_pass_recv_markers(Process *c_p,
 					  ErtsMessage **markpp);
-void erts_msgq_remove_leading_recv_markers(Process *c_p);
+void erts_msgq_remove_leading_recv_markers_set_save_first(Process *c_p);
 
 #define ERTS_RECV_MARKER_IX__(BLKP, MRKP) \
     ((int) ((MRKP) - &(BLKP)->marker[0]))
@@ -2112,8 +2112,9 @@ erts_msgq_set_save_first(Process *c_p)
      * anymore...
      */
     if (c_p->sig_qs.first && ERTS_SIG_IS_RECV_MARKER(c_p->sig_qs.first))
-	erts_msgq_remove_leading_recv_markers(c_p);
-    c_p->sig_qs.save = &c_p->sig_qs.first;
+	erts_msgq_remove_leading_recv_markers_set_save_first(c_p);
+    else
+        c_p->sig_qs.save = &c_p->sig_qs.first;
 }
 
 ERTS_GLB_INLINE void
diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index 393de2b7b1..00b6d16862 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -6631,10 +6631,12 @@ schedule_out_process(ErtsRunQueue *c_rq, erts_aint32_t state, Process *p,
              */
 
             /*
-             * No normal execution until dirty CLA or hibernat has
+             * No normal execution until dirty CLA or hibernate has
              * been handled...
              */
-            ASSERT(!(p->flags & (F_DIRTY_CLA | F_DIRTY_GC_HIBERNATE)));
+            ASSERT(!(p->flags & (F_DIRTY_CHECK_CLA
+                                 | F_DIRTY_CLA
+                                 | F_DIRTY_GC_HIBERNATE)));
 
             a = erts_atomic32_read_band_nob(&p->state,
                                             ~ERTS_PSFLG_DIRTY_ACTIVE_SYS);
@@ -10075,12 +10077,17 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls)
                      * continue exectution until the flush
                      * completes...
 		     */
-		    if (state & ERTS_PSFLGS_DIRTY_WORK)
-			sig_reds = reds;
-		    else if (p->sig_qs.flags & FS_FLUSHING_SIGS)
-                        sig_reds = reds;
-                    else
-			sig_reds = ERTS_SIG_HANDLE_REDS_MAX_PREFERED;
+                    sig_reds = reds;
+                    if (((state & (ERTS_PSFLGS_DIRTY_WORK
+                                   | ERTS_PSFLG_ACTIVE)) == ERTS_PSFLG_ACTIVE)
+                        && !(p->sig_qs.flags & FS_FLUSHING_SIGS)) {
+                        /*
+                         * We are active, i.e., have erlang work to do,
+                         * and have no dirty work and are not flushing
+                         * limit amount of signal handling work...
+                         */
+                        sig_reds = ERTS_SIG_HANDLE_REDS_MAX_PREFERED;
+                    }
 		    (void) erts_proc_sig_handle_incoming(p,
 							 &state,
 							 &sig_reds,
@@ -10600,25 +10607,49 @@ execute_sys_tasks(Process *c_p, erts_aint32_t *statep, int in_reds)
 	    int fcalls;
             int cla_reds = 0;
 
-	    if (!ERTS_PROC_GET_SAVED_CALLS_BUF(c_p))
-		fcalls = reds;
-	    else
-		fcalls = reds - CONTEXT_REDS;
-	    st_res = erts_copy_literals_gc(c_p, &cla_reds, fcalls);
-            reds -= cla_reds;
-	    if (is_non_value(st_res)) {
-		if (c_p->flags & F_DIRTY_CLA) {
-		    save_dirty_task(c_p, st);
-		    st = NULL;
-		    break;
-		}
-		/* Needed gc, but gc was disabled */
-		save_gc_task(c_p, st, st_prio);
-		st = NULL;
-		break;
-	    }
-            /* We did a major gc */
-            minor_gc = major_gc = 1;
+            if (st->arg[0] == am_true) {
+                /*
+                 * Check if copy literal area GC is needed and only
+                 * do GC if needed. This check is never requested unless
+                 * we know that this is to much work to do on a normal
+                 * scheduler, so we do not even try to check it here
+                 * but instead unconditionally schedule this as dirty
+                 * work...
+                 */
+                if (c_p->flags & F_DISABLE_GC) {
+                    /* We might need to GC, but GC was disabled */
+                    save_gc_task(c_p, st, st_prio);
+                    st = NULL;
+                }
+                else {
+                    c_p->flags |= F_DIRTY_CHECK_CLA;
+                    save_dirty_task(c_p, st);
+                    st = NULL;
+                    erts_schedule_dirty_sys_execution(c_p);
+                }
+            }
+            else {
+                /* Copy literal area GC needed... */
+                if (!ERTS_PROC_GET_SAVED_CALLS_BUF(c_p))
+                    fcalls = reds;
+                else
+                    fcalls = reds - CONTEXT_REDS;
+                st_res = erts_copy_literals_gc(c_p, &cla_reds, fcalls);
+                reds -= cla_reds;
+                if (is_non_value(st_res)) {
+                    if (c_p->flags & F_DIRTY_CLA) {
+                        save_dirty_task(c_p, st);
+                        st = NULL;
+                        break;
+                    }
+                    /* Needed gc, but gc was disabled */
+                    save_gc_task(c_p, st, st_prio);
+                    st = NULL;
+                    break;
+                }
+                /* We did a major gc */
+                minor_gc = major_gc = 1;
+            }
 	    break;
         }
         case ERTS_PSTT_FTMQ:
@@ -10823,10 +10854,12 @@ erts_execute_dirty_system_task(Process *c_p)
     /*
      * If multiple operations, perform them in the following
      * order (in order to avoid unnecessary GC):
-     *  1. Copy Literal Area (implies major GC).
-     *  2. GC Hibernate (implies major GC if not woken).
-     *  3. Major GC (implies minor GC).
-     *  4. Minor GC.
+     *  1. Check for Copy Literals Area GC need. This may
+     *     trigger a Copy Literals Area GC.
+     *  2. Copy Literal Area GC (implies major GC).
+     *  3. GC Hibernate (implies major GC if not woken).
+     *  4. Major GC (implies minor GC).
+     *  5. Minor GC.
      *
      * System task requests are handled after the actual
      * operations have been performed...
@@ -10834,6 +10867,37 @@ erts_execute_dirty_system_task(Process *c_p)
 
     ASSERT(!(c_p->flags & (F_DELAY_GC|F_DISABLE_GC)));
 
+    if (c_p->flags & F_DIRTY_CHECK_CLA) {
+        ErtsLiteralArea *la = ERTS_COPY_LITERAL_AREA();
+
+        ASSERT(!(c_p->flags & F_DIRTY_CLA));
+        c_p->flags &= ~F_DIRTY_CHECK_CLA;
+        if (!la)
+            cla_res = am_ok;
+        else {
+            int check_cla_reds = 0;
+            char *literals = (char *) &la->start[0];
+            Uint lit_bsize = (char *) la->end - literals;
+            if (erts_check_copy_literals_gc_need(c_p,
+                                                 &check_cla_reds,
+                                                 literals,
+                                                 lit_bsize)) {
+                /*
+                 * We had references to this literal area on the heap;
+                 * need a copy literals GC...
+                 */
+                c_p->flags |= F_DIRTY_CLA;
+            }
+            else {
+                /*
+                 * We have no references to this literal area on the
+                 * heap; no copy literals GC needed...
+                 */
+                cla_res = am_ok;
+            }
+        }
+    }
+
     if (c_p->flags & F_DIRTY_CLA) {
 	int cla_reds = 0;
         cla_res = erts_copy_literals_gc(c_p, &cla_reds, c_p->fcalls);
@@ -10862,7 +10926,8 @@ erts_execute_dirty_system_task(Process *c_p)
 					   c_p->arity, c_p->fcalls);
     }
 
-    ASSERT(!(c_p->flags & (F_DIRTY_CLA
+    ASSERT(!(c_p->flags & (F_DIRTY_CHECK_CLA
+                           | F_DIRTY_CLA
 			   | F_DIRTY_GC_HIBERNATE
 			   | F_DIRTY_MAJOR_GC
 			   | F_DIRTY_MINOR_GC)));
@@ -11246,7 +11311,7 @@ erts_internal_request_system_task_4(BIF_ALIST_4)
 }
 
 void
-erts_schedule_cla_gc(Process *c_p, Eterm to, Eterm req_id)
+erts_schedule_cla_gc(Process *c_p, Eterm to, Eterm req_id, int check)
 {
     Process *rp;
     ErtsProcSysTask *st;
@@ -11272,7 +11337,8 @@ erts_schedule_cla_gc(Process *c_p, Eterm to, Eterm req_id)
                                                        req_id_sz,
                                                        &hp,
                                                        &st->off_heap);
-    for (i = 0; i < ERTS_MAX_PROC_SYS_TASK_ARGS; i++)
+    st->arg[0] = check ? am_true : am_false;
+    for (i = 1; i < ERTS_MAX_PROC_SYS_TASK_ARGS; i++)
         st->arg[i] = THE_NON_VALUE;
 
     rp = erts_proc_lookup_raw(to);
diff --git a/erts/emulator/beam/erl_process.h b/erts/emulator/beam/erl_process.h
index 0459aeaba5..8dc55a8da0 100644
--- a/erts/emulator/beam/erl_process.h
+++ b/erts/emulator/beam/erl_process.h
@@ -1568,6 +1568,7 @@ extern int erts_system_profile_ts_type;
 #define F_TRAP_EXIT          (1 << 22) /* Trapping exit */
 #define F_FRAGMENTED_SEND    (1 << 23) /* Process is doing a distributed fragmented send */
 #define F_DBG_FORCED_TRAP    (1 << 24) /* DEBUG: Last BIF call was a forced trap */
+#define F_DIRTY_CHECK_CLA    (1 << 25) /* Check if copy literal area GC scheduled */
 
 /* Signal queue flags */
 #define FS_OFF_HEAP_MSGQ       (1 << 0) /* Off heap msg queue */
@@ -1934,7 +1935,7 @@ void erts_schedule_thr_prgr_later_cleanup_op(void (*)(void *),
 					     ErtsThrPrgrLaterOp *,
 					     UWord);
 void erts_schedule_complete_off_heap_message_queue_change(Eterm pid);
-void erts_schedule_cla_gc(Process *c_p, Eterm to, Eterm req_id);
+void erts_schedule_cla_gc(Process *c_p, Eterm to, Eterm req_id, int check);
 struct db_fixation;
 void erts_schedule_ets_free_fixation(Eterm pid, struct db_fixation*);
 void erts_schedule_flush_trace_messages(Process *proc, int force_on_proc);
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index f892d0dd89..f54596cf58 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -957,6 +957,7 @@ Eterm erl_is_function(Process* p, Eterm arg1, Eterm arg2);
 Eterm erts_check_process_code(Process *c_p, Eterm module, int *redsp, int fcalls);
 #define ERTS_CLA_SCAN_WORDS_PER_RED 512
 
+int erts_check_copy_literals_gc_need_max_reds(Process *c_p);
 int erts_check_copy_literals_gc_need(Process *c_p, int *redsp,
                                      char *literals, Uint lit_bsize);
 Eterm erts_copy_literals_gc(Process *c_p, int *redsp, int fcalls);
diff --git a/erts/emulator/test/literal_area_collector_test.erl b/erts/emulator/test/literal_area_collector_test.erl
index 14583db88d..d0b6fb3822 100644
--- a/erts/emulator/test/literal_area_collector_test.erl
+++ b/erts/emulator/test/literal_area_collector_test.erl
@@ -28,38 +28,29 @@ check_idle(Timeout) when is_integer(Timeout) > 0 ->
     ScaledTimeout = Timeout*test_server:timetrap_scale_factor(),
     Pid = find_literal_area_collector(),
     Start = erlang:monotonic_time(millisecond),
-    try
-        wait_for_idle_literal_collector(Pid, Start, ScaledTimeout, -1, 0)
-    catch
-        throw:done ->
-            ok
-    end.
+    Alias = alias(),
+    wait_for_idle_literal_collector(Pid, Alias, Start, ScaledTimeout).
 
-wait_for_idle_literal_collector(Pid, Start, Timeout, NWaiting, WRedsStart) ->
-    {W, R} = case process_info(Pid, [status, reductions]) of
-                 [{status, waiting}, {reductions, Reds}] ->
-                     %% Assume that reds aren't bumped more than
-                     %% 2 in order to service this process info
-                     %% request...
-                     case {NWaiting > 100, Reds - WRedsStart =< 2*NWaiting} of
-                         {true, true} ->
-                             throw(done);
-                         {false, true} ->
-                             {NWaiting+1, WRedsStart};
-                         _ ->
-                             {0, Reds}
-                     end;
-                 _ ->
-                     {-1, 0}
-             end,
+wait_for_idle_literal_collector(Pid, Alias, Start, Timeout) ->
+    Ref = make_ref(),
+    Pid ! {get_status, Ref, Alias},
     Now = erlang:monotonic_time(millisecond),
-    if Now - Start > Timeout ->
-            error({busy_literal_area_collecor_timout, Timeout});
-       true ->
-            ok
-    end,
-    receive after 1 -> ok end,
-    wait_for_idle_literal_collector(Pid, Start, Timeout, W, R).
+    TMO = case Start + Timeout - Now of
+              TimeLeft when TimeLeft < 0 -> 0;
+              TimeLeft -> TimeLeft
+          end,
+    receive
+        {Ref, idle} ->
+            unalias(Alias),
+            ok;
+        {Ref, _} ->
+            receive after 10 -> ok end,
+            wait_for_idle_literal_collector(Pid, Alias, Start, Timeout)
+    after TMO ->
+            unalias(Alias),
+            receive {Ref, _} -> ok after 0 -> ok end,
+            error({busy_literal_area_collecor_timout, Timeout})
+    end.
     
 find_literal_area_collector() ->
     case get('__literal_area_collector__') of
diff --git a/erts/emulator/test/signal_SUITE.erl b/erts/emulator/test/signal_SUITE.erl
index e1fcd3fbd4..ec2cbfb80e 100644
--- a/erts/emulator/test/signal_SUITE.erl
+++ b/erts/emulator/test/signal_SUITE.erl
@@ -32,6 +32,7 @@
 -include_lib("common_test/include/ct.hrl").
 -export([all/0, suite/0,init_per_suite/1, end_per_suite/1]).
 -export([init_per_testcase/2, end_per_testcase/2]).
+-export([groups/0, init_per_group/2, end_per_group/2]).
 
 % Test cases
 -export([xm_sig_order/1,
@@ -43,7 +43,19 @@
          busy_dist_spawn_reply_signal/1,
          busy_dist_unlink_ack_signal/1,
          unlink_exit/1,
-         monitor_order/1]).
+         monitor_order/1,
+         move_msgs_off_heap_signal_basic/1,
+         move_msgs_off_heap_signal_recv/1,
+         move_msgs_off_heap_signal_exit/1,
+         move_msgs_off_heap_signal_recv_exit/1,
+         copy_literal_area_signal_basic/1,
+         copy_literal_area_signal_recv/1,
+         copy_literal_area_signal_exit/1,
+         copy_literal_area_signal_recv_exit/1,
+         simultaneous_signals_basic/1,
+         simultaneous_signals_recv/1,
+         simultaneous_signals_exit/1,
+         simultaneous_signals_recv_exit/1]).
 
 init_per_testcase(Func, Config) when is_atom(Func), is_list(Config) ->
     [{testcase, Func}|Config].
@@ -71,7 +83,29 @@ all() ->
      busy_dist_spawn_reply_signal,
      busy_dist_unlink_ack_signal,
      unlink_exit,
-     monitor_order].
+     monitor_order,
+     {group, adjust_message_queue}].
+
+groups() ->
+    [{adjust_message_queue, [],
+      [move_msgs_off_heap_signal_basic,
+       move_msgs_off_heap_signal_recv,
+       move_msgs_off_heap_signal_exit,
+       move_msgs_off_heap_signal_recv_exit,
+       copy_literal_area_signal_basic,
+       copy_literal_area_signal_recv,
+       copy_literal_area_signal_exit,
+       copy_literal_area_signal_recv_exit,
+       simultaneous_signals_basic,
+       simultaneous_signals_recv,
+       simultaneous_signals_exit,
+       simultaneous_signals_recv_exit]}].
+
+init_per_group(_GroupName, Config) ->
+    Config.
+
+end_per_group(_GroupName, Config) ->
+    Config.
 
 %% Test that exit signals and messages are received in correct order
 xm_sig_order(Config) when is_list(Config) ->
@@ -588,6 +622,282 @@ monitor_order_1(N) ->
             monitor_order_1(N - 1)
     end.
 
+move_msgs_off_heap_signal_basic(Config) when is_list(Config) ->
+    move_msgs_off_heap_signal_test(false, false).
+
+move_msgs_off_heap_signal_recv(Config) when is_list(Config) ->
+    move_msgs_off_heap_signal_test(true, false).
+
+move_msgs_off_heap_signal_exit(Config) when is_list(Config) ->
+    move_msgs_off_heap_signal_test(false, true).
+
+move_msgs_off_heap_signal_recv_exit(Config) when is_list(Config) ->
+    move_msgs_off_heap_signal_test(true, true).
+
+move_msgs_off_heap_signal_test(RecvPair, Exit) ->
+    erlang:trace(new_processes, true, [running_procs]),
+    SFact = test_server:timetrap_scale_factor(),
+    GoTime = erlang:monotonic_time(millisecond) + 1000*SFact,
+    ProcF = fun () ->
+                    Now = erlang:monotonic_time(millisecond),
+                    Tmo = case GoTime - Now of
+                              Left when Left < 0 ->
+                                  erlang:display({go_time_passed, Left}),
+                                  0;
+                              Left ->
+                                  Left
+                          end,
+                    receive after Tmo -> ok end,
+                    on_heap = process_flag(message_queue_data, off_heap),
+                    if RecvPair -> receive_integer_pairs(infinity);
+                       true -> receive after infinity -> ok end
+                    end
+            end,
+    Ps = lists:map(fun (_) ->
+                           spawn_opt(ProcF,
+                                     [link,
+                                      {message_queue_data, on_heap}])
+                   end, lists:seq(1, 100)),
+    lists:foreach(fun (P) ->
+                          lists:foreach(fun (N) when N rem 100 == 0 ->
+                                                P ! [N|N];
+                                            (N) ->
+                                                P ! N
+                                        end, lists:seq(1, 10000))
+                  end, Ps),
+    Now = erlang:monotonic_time(millisecond),
+    Tmo = case GoTime - Now + 10 of
+              Left when Left < 0 ->
+                  erlang:display({go_time_passed, Left}),
+                  0;
+              Left ->
+                  Left
+          end,
+    receive after Tmo -> ok end,
+    if Exit ->
+            _ = lists:foldl(fun (P, N) when N rem 10 ->
+                                    unlink(P),
+                                    exit(P, terminated),
+                                    N+1;
+                                (_P, N) ->
+                                    N+1
+                            end,
+                            0,
+                            Ps),
+            ok;
+       true ->
+            ok
+    end,
+    wait_traced_not_running(1000 + 200*SFact),
+    erlang:trace(new_processes, false, [running_procs]),
+    lists:foreach(fun (P) ->
+                          unlink(P),
+                          exit(P, kill)
+                  end, Ps),
+    lists:foreach(fun (P) ->
+                          false = is_process_alive(P)
+                  end, Ps),
+    ok.
+
+copy_literal_area_signal_basic(Config) when is_list(Config) ->
+    copy_literal_area_signal_test(false, false).
+
+copy_literal_area_signal_recv(Config) when is_list(Config) ->
+    copy_literal_area_signal_test(true, false).
+
+copy_literal_area_signal_exit(Config) when is_list(Config) ->
+    copy_literal_area_signal_test(false, true).
+
+copy_literal_area_signal_recv_exit(Config) when is_list(Config) ->
+    copy_literal_area_signal_test(true, true).
+
+copy_literal_area_signal_test(RecvPair, Exit) ->
+    persistent_term:put({?MODULE, ?FUNCTION_NAME}, make_ref()),
+    Literal = persistent_term:get({?MODULE, ?FUNCTION_NAME}),
+    true = is_reference(Literal),
+    0 = erts_debug:size_shared(Literal), %% Should be a literal...
+    ProcF = fun () ->
+                    0 = erts_debug:size_shared(Literal), %% Should be a literal...
+                    if RecvPair ->
+                            receive receive_pairs -> ok end,
+                            receive_integer_pairs(0);
+                       true ->
+                            ok
+                    end,
+                    receive check_literal_conversion -> ok end,
+                    receive
+                        Literal ->
+                            %% Should not be a literal anymore...
+                            false = (0 == erts_debug:size_shared(Literal))
+                    end
+            end,
+    PMs = lists:map(fun (_) ->
+                            spawn_opt(ProcF, [link, monitor])
+                    end, lists:seq(1, 100)),
+    lists:foreach(fun ({P,_M}) ->
+                          lists:foreach(fun (N) when N rem 100 == 0 ->
+                                                P ! [N|N];
+                                            (N) ->
+                                                P ! N
+                                        end, lists:seq(1, 10000)),
+                          P ! Literal
+                  end, PMs),
+    persistent_term:erase({?MODULE, ?FUNCTION_NAME}),
+    receive after 1 -> ok end,
+    if RecvPair ->
+            lists:foreach(fun ({P,_M}) ->
+                                  P ! receive_pairs
+                          end, PMs);
+       true ->
+            ok
+    end,
+    if Exit ->
+            _ = lists:foldl(fun ({P, _M}, N) when N rem 10 ->
+                                    unlink(P),
+                                    exit(P, terminated),
+                                    N+1;
+                                (_PM, N) ->
+                                    N+1
+                            end,
+                            0,
+                            PMs),
+            ok;
+       true ->
+            ok
+    end,
+    literal_area_collector_test:check_idle(),
+    lists:foreach(fun ({P,_M}) ->
+                          P ! check_literal_conversion
+                  end, PMs),
+    lists:foreach(fun ({P, M}) ->
+                          receive
+                              {'DOWN', M, process, P, R} ->
+                                  case R of
+                                      normal -> ok;
+                                      terminated -> ok
+                                  end
+                          end
+                  end, PMs),
+    ok.
+
+simultaneous_signals_basic(Config) when is_list(Config) ->
+    simultaneous_signals_test(false, false).
+
+simultaneous_signals_recv(Config) when is_list(Config) ->
+    simultaneous_signals_test(true, false).
+
+simultaneous_signals_exit(Config) when is_list(Config) ->
+    simultaneous_signals_test(false, true).
+
+simultaneous_signals_recv_exit(Config) when is_list(Config) ->
+    simultaneous_signals_test(true, true).
+
+simultaneous_signals_test(RecvPairs, Exit) ->
+    erlang:trace(new_processes, true, [running_procs]),
+    persistent_term:put({?MODULE, ?FUNCTION_NAME}, make_ref()),
+    Literal = persistent_term:get({?MODULE, ?FUNCTION_NAME}),
+    true = is_reference(Literal),
+    0 = erts_debug:size_shared(Literal), %% Should be a literal...
+    SFact = test_server:timetrap_scale_factor(),
+    GoTime = erlang:monotonic_time(millisecond) + 1000*SFact,
+    ProcF = fun () ->
+                    0 = erts_debug:size_shared(Literal), %% Should be a literal...
+                    Now = erlang:monotonic_time(millisecond),
+                    Tmo = case GoTime - Now of
+                              Left when Left < 0 ->
+                                  erlang:display({go_time_passed, Left}),
+                                  0;
+                              Left ->
+                                  Left
+                          end,
+                    receive after Tmo -> ok end,
+                    on_heap = process_flag(message_queue_data, off_heap),
+                    if RecvPairs -> receive_integer_pairs(0);
+                       true -> ok
+                    end,
+                    receive check_literal_conversion -> ok end,
+                    receive
+                        Literal ->
+                            %% Should not be a literal anymore...
+                            false = (0 == erts_debug:size_shared(Literal))
+                    end
+            end,
+    PMs = lists:map(fun (_) ->
+                            spawn_opt(ProcF,
+                                      [link,
+                                       monitor,
+                                       {message_queue_data, on_heap}])
+                    end, lists:seq(1, 100)),
+    lists:foreach(fun ({P,_M}) ->
+                          lists:foreach(fun (N) when N rem 100 == 0 ->
+                                                P ! [N|N];
+                                            (N) ->
+                                                P ! N
+                                        end, lists:seq(1, 10000)),
+                          P ! Literal
+                  end, PMs),
+    Now = erlang:monotonic_time(millisecond),
+    Tmo = case GoTime - Now - 5 of % a bit earlier...
+              Left when Left < 0 ->
+                  erlang:display({go_time_passed, Left}),
+                  0;
+              Left ->
+                  Left
+          end,
+    receive after Tmo -> ok end,
+    persistent_term:erase({?MODULE, ?FUNCTION_NAME}),
+    receive after 10 -> ok end,
+    if Exit ->
+            _ = lists:foldl(fun ({P, _M}, N) when N rem 10 ->
+                                    unlink(P),
+                                    exit(P, terminated),
+                                    N+1;
+                                (_PM, N) ->
+                                    N+1
+                            end,
+                            0,
+                            PMs),
+            ok;
+       true ->
+            ok
+    end,
+    wait_traced_not_running(1000 + 200*SFact),
+    erlang:trace(new_processes, false, [running_procs]),
+    literal_area_collector_test:check_idle(),
+    lists:foreach(fun ({P,_M}) ->
+                          P ! check_literal_conversion
+                  end, PMs),
+    lists:foreach(fun ({P, M}) ->
+                          receive
+                              {'DOWN', M, process, P, R} ->
+                                  case R of
+                                      normal -> ok;
+                                      terminated -> ok
+                                  end
+                          end
+                  end, PMs),
+    ok.
+    
+
+wait_traced_not_running(Tmo) ->
+    receive
+        {trace,_,What,_} when What == in;
+                              What == out ->
+            wait_traced_not_running(Tmo)
+    after
+        Tmo ->
+            ok
+    end.
+
+receive_integer_pairs(Tmo) ->
+    receive
+        [N|N] ->
+            receive_integer_pairs(Tmo)
+    after
+        Tmo ->
+            ok
+    end.
+
 %%
 %% -- Internal utils --------------------------------------------------------
 %%
diff --git a/erts/preloaded/src/erts_literal_area_collector.erl b/erts/preloaded/src/erts_literal_area_collector.erl
index 8a73ed1685..bb2ad6b919 100644
--- a/erts/preloaded/src/erts_literal_area_collector.erl
+++ b/erts/preloaded/src/erts_literal_area_collector.erl
@@ -62,39 +62,46 @@ msg_loop(Area, {Ongoing, NeedIReq} = OReqInfo, GcOutstnd, NeedGC) ->
 	    switch_area();
 
 	%% Process (_Pid) has completed the request...
-	{copy_literals, {Area, _GcAllowed, _Pid}, ok} when Ongoing == 1,
-                                                           NeedIReq == [] ->
+	{copy_literals, {Area, _ReqType, _Pid}, ok} when Ongoing == 1,
+                                                         NeedIReq == [] ->
 	    switch_area(); %% Last process completed...
-	{copy_literals, {Area, false, _Pid}, ok} ->
+	{copy_literals, {Area, init, _Pid}, ok} ->
 	    msg_loop(Area, check_send_copy_req(Area, Ongoing-1, NeedIReq),
                      GcOutstnd, NeedGC);
-	{copy_literals, {Area, true, _Pid}, ok} when NeedGC == [] ->
+	{copy_literals, {Area, ReqType, _Pid}, ok} when NeedGC == [],
+                                                        ReqType /= init ->
 	    msg_loop(Area, check_send_copy_req(Area, Ongoing-1, NeedIReq),
                      GcOutstnd-1, []);
-	{copy_literals, {Area, true, _Pid}, ok} ->
-	    send_copy_req(hd(NeedGC), Area, true),
-	    msg_loop(Area, {Ongoing-1, NeedIReq}, GcOutstnd, tl(NeedGC));
+	{copy_literals, {Area, ReqType, _Pid}, ok} when ReqType /= init ->
+            [{GCPid,GCWork} | NewNeedGC] = NeedGC,
+	    send_copy_req(GCPid, Area, GCWork),
+	    msg_loop(Area, {Ongoing-1, NeedIReq}, GcOutstnd, NewNeedGC);
 
 	%% Process (Pid) failed to complete the request
 	%% since it needs to garbage collect in order to
 	%% complete the request...
-	{copy_literals, {Area, false, Pid}, need_gc} when GcOutstnd < ?MAX_GC_OUTSTND ->
-	    send_copy_req(Pid, Area, true),
+	{copy_literals, {Area, init, Pid}, GCWork} when GcOutstnd
+                                                        < ?MAX_GC_OUTSTND ->
+	    send_copy_req(Pid, Area, GCWork),
 	    msg_loop(Area, OReqInfo, GcOutstnd+1, NeedGC);
-	{copy_literals, {Area, false, Pid}, need_gc} ->
+	{copy_literals, {Area, init, Pid}, GCWork} ->
 	    msg_loop(Area, check_send_copy_req(Area, Ongoing, NeedIReq),
-                     GcOutstnd, [Pid|NeedGC]);
+                     GcOutstnd, [{Pid,GCWork} | NeedGC]);
 
 	%% Not handled message regarding the area that we
 	%% currently are working with. Crash the VM so
 	%% we notice this bug...
-	{copy_literals, {Area, _, _}, _} = Msg when erlang:is_reference(Area) ->
+	{copy_literals, {Area, _, _}, _} = Msg ->
 	    exit({not_handled_message, Msg});
 
         {change_prio, From, Ref, Prio} ->
             change_prio(From, Ref, Prio),
 	    msg_loop(Area, OReqInfo, GcOutstnd, NeedGC);
 
+        {get_status, Ref, From} when is_pid(From); is_reference(From) ->
+            From ! {Ref, if Ongoing == 0 -> idle; true -> working end},
+            msg_loop(Area, OReqInfo, GcOutstnd, NeedGC);
+
 	%% Unexpected garbage message. Get rid of it...
 	_Ignore ->
 	    msg_loop(Area, OReqInfo, GcOutstnd, NeedGC)
@@ -126,7 +133,7 @@ switch_area() ->
 check_send_copy_req(_Area, Ongoing, []) ->
     {Ongoing, []};
 check_send_copy_req(Area, Ongoing, [Pid|Pids]) ->
-    send_copy_req(Pid, Area, false),
+    send_copy_req(Pid, Area, init),
     {Ongoing+1, Pids}.
 
 send_copy_reqs(Ps, Area, OReqLim) ->
@@ -137,23 +144,23 @@ send_copy_reqs([], _Area, _OReqLim, N) ->
 send_copy_reqs(Ps, _Area, OReqLim, N) when N >= OReqLim ->
     {N, Ps};
 send_copy_reqs([P|Ps], Area, OReqLim, N) ->
-    send_copy_req(P, Area, false),
+    send_copy_req(P, Area, init),
     send_copy_reqs(Ps, Area, OReqLim, N+1).
 
-send_copy_req(P, Area, GC) ->
-    erts_literal_area_collector:send_copy_request(P, Area, GC).
+send_copy_req(P, Area, How) ->
+    erts_literal_area_collector:send_copy_request(P, Area, How).
 
 -spec release_area_switch() -> boolean().
 
 release_area_switch() ->
     erlang:nif_error(undef). %% Implemented in beam_bif_load.c
 
--spec send_copy_request(To, AreaId, GcAllowed) -> 'ok' when
+-spec send_copy_request(To, AreaId, How) -> 'ok' when
       To :: pid(),
       AreaId :: term(),
-      GcAllowed :: boolean().
+      How :: 'init' | 'check_gc' | 'need_gc'.
 
-send_copy_request(_To, _AreaId, _GcAllowed) ->
+send_copy_request(_To, _AreaId, _How) ->
     erlang:nif_error(undef). %% Implemented in beam_bif_load.c
 
 change_prio(From, Ref, Prio) ->
-- 
2.35.3

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File 4032-erts-Yield-when-adjusting-large-message-queues.patch of Package erlang (Revision b2172ea35270b4e41324f000c94154cb)

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