Changeset 3118355 in mainline for kernel/generic/src/proc/scheduler.c

Timestamp:

2023-03-21T17:41:48Z (13 months ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

master, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

c680333

Parents:

72ac106

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2023-02-26 17:56:29)

git-committer:

Jiří Zárevúcky <zarevucky.jiri@…> (2023-03-21 17:41:48)

Message:

Optimize relink_rq()

Iterate backwards and only lock each runqueue once instead of twice.

File:

• kernel/generic/src/proc/scheduler.c (modified) (1 diff)

kernel/generic/src/proc/scheduler.c

@@ -275 +275 @@
         CPU->relink_deadline = CPU->current_clock_tick + NEEDS_RELINK_MAX;
 
+        /* Temporary cache for lists we are moving. */
         list_t list;
         list_initialize(&list);
 
+        size_t n = 0;
+
         irq_spinlock_lock(&CPU->lock, false);
 
-        for (int i = start; i < RQ_COUNT - 1; i++) {
-                /* Remember and empty rq[i + 1] */
-
-                irq_spinlock_lock(&CPU->rq[i + 1].lock, false);
-                list_concat(&list, &CPU->rq[i + 1].rq);
-                size_t n = CPU->rq[i + 1].n;
-                CPU->rq[i + 1].n = 0;
-                irq_spinlock_unlock(&CPU->rq[i + 1].lock, false);
-
-                /* Append rq[i + 1] to rq[i] */
-
+        /* Move every list (except the one with highest priority) one level up. */
+        for (int i = RQ_COUNT - 1; i > start; i--) {
                 irq_spinlock_lock(&CPU->rq[i].lock, false);
-                list_concat(&CPU->rq[i].rq, &list);
-                CPU->rq[i].n += n;
+
+                /* Swap lists. */
+                list_swap(&CPU->rq[i].rq, &list);
+
+                /* Swap number of items. */
+                size_t tmpn = CPU->rq[i].n;
+                CPU->rq[i].n = n;
+                n = tmpn;
+
                 irq_spinlock_unlock(&CPU->rq[i].lock, false);
+        }
+
+        /* Append the contents of rq[start + 1]  to rq[start]. */
+        if (n != 0) {
+                irq_spinlock_lock(&CPU->rq[start].lock, false);
+                list_concat(&CPU->rq[start].rq, &list);
+                CPU->rq[start].n += n;
+                irq_spinlock_unlock(&CPU->rq[start].lock, false);
         }