File 6702-Trivial-refactoring-of-try_steal_task.patch of Package erlang

From 110ff4aaa8e84f824eb015a7d442d1a3d025c813 Mon Sep 17 00:00:00 2001
From: Robin Morisset <rmorisset@meta.com>
Date: Mon, 14 Apr 2025 01:50:24 -0700
Subject: [PATCH 2/4] Trivial refactoring of try_steal_task

---
 erts/emulator/beam/erl_process.c | 87 ++++++++++++++++----------------
 1 file changed, 44 insertions(+), 43 deletions(-)

diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index 536750116d..f09ff0adda 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -4647,7 +4647,7 @@ try_steal_task(ErtsRunQueue *rq, Process **result_proc)
 
     flags = empty_runq_get_old_flags(rq);
     if (flags & ERTS_RUNQ_FLG_SUSPENDED)
-	return 0; /* go suspend instead... */
+        return 0; /* go suspend instead... */
 
     ERTS_LC_ASSERT(erts_lc_runq_is_locked(rq));
     erts_runq_unlock(rq);
@@ -4655,57 +4655,58 @@ try_steal_task(ErtsRunQueue *rq, Process **result_proc)
     get_no_runqs(&active_rqs, &blnc_rqs);
 
     if (active_rqs > blnc_rqs)
-	active_rqs = blnc_rqs;
+        active_rqs = blnc_rqs;
 
     if (erts_atomic32_read_acqb(&no_empty_run_queues) >= blnc_rqs)
         goto end_try_steal_task;
 
-    if (rq->ix < active_rqs) {
-	/* First try to steal from an inactive run queue... */
-	if (active_rqs < blnc_rqs) {
-	    int no = blnc_rqs - active_rqs;
-	    int stop_ix = vix = active_rqs + rq->ix % no;
-	    while (1) {
-		res = check_possible_steal_victim(rq, vix, result_proc, &contended_runqueues);
-		if (res) {
-                    DESTROY_WSTACK(contended_runqueues);
-                    return res;
-                }
-		vix++;
-		if (vix >= blnc_rqs)
-		    vix = active_rqs;
-		if (vix == stop_ix)
-		    break;
-	    }
-	}
-
-	vix = rq->ix;
-
-	/* ... then try to steal a job from another active queue... */
-	while (1) {
-	    vix++;
-	    if (vix >= active_rqs)
-		vix = 0;
-	    if (vix == rq->ix)
-		break;
-
-	    res = check_possible_steal_victim(rq, vix, result_proc, &contended_runqueues);
-	    if (res) {
-                DESTROY_WSTACK(contended_runqueues);
-                return res;
-            }
-	}
+    if (rq->ix >= active_rqs)
+        goto end_try_steal_task;
 
-        /* ... and finally re-try stealing from the queues that were skipped because contended.
-           We recheck the number of empty runqueues in each iteration, as taking the runqueue lock in check_possible_steal_victim can take quite a while. */
-        while (!WSTACK_ISEMPTY(contended_runqueues)
-                && (erts_atomic32_read_acqb(&no_empty_run_queues) < blnc_rqs)) {
-            vix = WSTACK_POP(contended_runqueues);
-            res = check_possible_steal_victim(rq, vix, result_proc, NULL);
+    /* First try to steal from an inactive run queue... */
+    if (active_rqs < blnc_rqs) {
+        int no = blnc_rqs - active_rqs;
+        int stop_ix = vix = active_rqs + rq->ix % no;
+        while (1) {
+            res = check_possible_steal_victim(rq, vix, result_proc, &contended_runqueues);
             if (res) {
                 DESTROY_WSTACK(contended_runqueues);
                 return res;
             }
+            vix++;
+            if (vix >= blnc_rqs)
+                vix = active_rqs;
+            if (vix == stop_ix)
+                break;
+        }
+    }
+
+    vix = rq->ix;
+
+    /* ... then try to steal a job from another active queue... */
+    while (1) {
+        vix++;
+        if (vix >= active_rqs)
+            vix = 0;
+        if (vix == rq->ix)
+            break;
+
+        res = check_possible_steal_victim(rq, vix, result_proc, &contended_runqueues);
+        if (res) {
+            DESTROY_WSTACK(contended_runqueues);
+            return res;
+        }
+    }
+
+    /* ... and finally re-try stealing from the queues that were skipped because contended.
+            We recheck the number of empty runqueues in each iteration, as taking the runqueue lock in check_possible_steal_victim can take quite a while. */
+    while (!WSTACK_ISEMPTY(contended_runqueues)
+            && (erts_atomic32_read_acqb(&no_empty_run_queues) < blnc_rqs)) {
+        vix = WSTACK_POP(contended_runqueues);
+        res = check_possible_steal_victim(rq, vix, result_proc, NULL);
+        if (res) {
+            DESTROY_WSTACK(contended_runqueues);
+            return res;
         }
     }
 
-- 
2.51.0