Changeset 011c79a in mainline for kernel/generic/src/proc/scheduler.c

Timestamp:

2023-02-04T16:19:33Z (15 months ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

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

Children:

e86f568

Parents:

aae2869

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2022-08-16 11:19:14)

git-committer:

Jiří Zárevúcky <zarevucky.jiri@…> (2023-02-04 16:19:33)

Message:

Replace CPU→needs_relink with CPU→relink_deadline

This removes a bit of unnecessary locking in clock().

File:

• kernel/generic/src/proc/scheduler.c (modified) (2 diffs)

kernel/generic/src/proc/scheduler.c

@@ -270 +270 @@
 static void relink_rq(int start)
 {
+        if (CPU->current_clock_tick < CPU->relink_deadline)
+                return;
+
+        CPU->relink_deadline = CPU->current_clock_tick + NEEDS_RELINK_MAX;
+
         list_t list;
-
         list_initialize(&list);
+
         irq_spinlock_lock(&CPU->lock, false);
 
-        if (CPU->needs_relink > NEEDS_RELINK_MAX) {
-                int i;
-                for (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] */
-
-                        irq_spinlock_lock(&CPU->rq[i].lock, false);
-                        list_concat(&CPU->rq[i].rq, &list);
-                        CPU->rq[i].n += n;
-                        irq_spinlock_unlock(&CPU->rq[i].lock, false);
-                }
-
-                CPU->needs_relink = 0;
+        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] */
+
+                irq_spinlock_lock(&CPU->rq[i].lock, false);
+                list_concat(&CPU->rq[i].rq, &list);
+                CPU->rq[i].n += n;
+                irq_spinlock_unlock(&CPU->rq[i].lock, false);
         }
 
@@ -726 +726 @@
                 irq_spinlock_lock(&cpus[cpu].lock, true);
 
-                printf("cpu%u: address=%p, nrdy=%zu, needs_relink=%zu\n",
+                /* Technically a data race, but we don't really care in this case. */
+                int needs_relink = cpus[cpu].relink_deadline - cpus[cpu].current_clock_tick;
+
+                printf("cpu%u: address=%p, nrdy=%zu, needs_relink=%d\n",
                     cpus[cpu].id, &cpus[cpu], atomic_load(&cpus[cpu].nrdy),
-                    cpus[cpu].needs_relink);
+                    needs_relink);
 
                 unsigned int i;