Changeset fbaf6ac in mainline

Timestamp:

2023-04-16T12:39:04Z (18 months ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

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

Children:

06f81c4

Parents:

169815e

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2023-03-27 17:01:08)

git-committer:

Jiří Zárevúcky <zarevucky.jiri@…> (2023-04-16 12:39:04)

Message:

Streamline thread load-balancing

Location:

kernel/generic/src/proc

Files:

• scheduler.c (modified) (3 diffs)
• thread.c (modified) (1 diff)

kernel/generic/src/proc/scheduler.c

@@ -502 +502 @@
 
 #ifdef CONFIG_SMP
+
+static thread_t *steal_thread_from(cpu_t *old_cpu, int i)
+{
+        runq_t *old_rq = &old_cpu->rq[i];
+        runq_t *new_rq = &CPU->rq[i];
+
+        irq_spinlock_lock(&old_rq->lock, true);
+
+        /* Search rq from the back */
+        list_foreach_rev(old_rq->rq, rq_link, thread_t, thread) {
+
+                irq_spinlock_lock(&thread->lock, false);
+
+                /*
+                 * Do not steal CPU-wired threads, threads
+                 * already stolen, threads for which migration
+                 * was temporarily disabled or threads whose
+                 * FPU context is still in the CPU.
+                 */
+                if (thread->stolen || thread->nomigrate || thread->fpu_context_engaged) {
+                        irq_spinlock_unlock(&thread->lock, false);
+                        continue;
+                }
+
+                thread->stolen = true;
+                thread->cpu = CPU;
+
+                irq_spinlock_unlock(&thread->lock, false);
+
+                /*
+                 * Ready thread on local CPU
+                 */
+
+#ifdef KCPULB_VERBOSE
+                log(LF_OTHER, LVL_DEBUG,
+                    "kcpulb%u: TID %" PRIu64 " -> cpu%u, "
+                    "nrdy=%ld, avg=%ld", CPU->id, thread->tid,
+                    CPU->id, atomic_load(&CPU->nrdy),
+                    atomic_load(&nrdy) / config.cpu_active);
+#endif
+
+                /* Remove thread from ready queue. */
+                old_rq->n--;
+                list_remove(&thread->rq_link);
+
+                irq_spinlock_pass(&old_rq->lock, &new_rq->lock);
+
+                /* Append thread to local queue. */
+                list_append(&thread->rq_link, &new_rq->rq);
+                new_rq->n++;
+
+                irq_spinlock_unlock(&new_rq->lock, true);
+
+                atomic_dec(&old_cpu->nrdy);
+                atomic_inc(&CPU->nrdy);
+
+                return thread;
+        }
+
+        irq_spinlock_unlock(&old_rq->lock, true);
+        return NULL;
+}
+
 /** Load balancing thread
  *
@@ -541 +604 @@
          */
         size_t acpu;
-        size_t acpu_bias = 0;
         int rq;
 
         for (rq = RQ_COUNT - 1; rq >= 0; rq--) {
                 for (acpu = 0; acpu < config.cpu_active; acpu++) {
-                        cpu_t *cpu = &cpus[(acpu + acpu_bias) % config.cpu_active];
+                        cpu_t *cpu = &cpus[acpu];
 
                         /*
@@ -560 +622 @@
                                 continue;
 
-                        irq_spinlock_lock(&(cpu->rq[rq].lock), true);
-                        if (cpu->rq[rq].n == 0) {
-                                irq_spinlock_unlock(&(cpu->rq[rq].lock), true);
-                                continue;
-                        }
-
-                        thread_t *thread = NULL;
-
-                        /* Search rq from the back */
-                        link_t *link = list_last(&cpu->rq[rq].rq);
-
-                        while (link != NULL) {
-                                thread = (thread_t *) list_get_instance(link,
-                                    thread_t, rq_link);
-
-                                /*
-                                 * Do not steal CPU-wired threads, threads
-                                 * already stolen, threads for which migration
-                                 * was temporarily disabled or threads whose
-                                 * FPU context is still in the CPU.
-                                 */
-                                irq_spinlock_lock(&thread->lock, false);
-
-                                if ((!thread->stolen) &&
-                                    (!thread->nomigrate) &&
-                                    (!thread->fpu_context_engaged)) {
-                                        /*
-                                         * Remove thread from ready queue.
-                                         */
-                                        irq_spinlock_unlock(&thread->lock,
-                                            false);
-
-                                        atomic_dec(&cpu->nrdy);
-                                        atomic_dec(&nrdy);
-
-                                        cpu->rq[rq].n--;
-                                        list_remove(&thread->rq_link);
-
-                                        break;
-                                }
-
-                                irq_spinlock_unlock(&thread->lock, false);
-
-                                link = list_prev(link, &cpu->rq[rq].rq);
-                                thread = NULL;
-                        }
-
-                        if (thread) {
-                                /*
-                                 * Ready thread on local CPU
-                                 */
-
-                                irq_spinlock_pass(&(cpu->rq[rq].lock),
-                                    &thread->lock);
-
-#ifdef KCPULB_VERBOSE
-                                log(LF_OTHER, LVL_DEBUG,
-                                    "kcpulb%u: TID %" PRIu64 " -> cpu%u, "
-                                    "nrdy=%ld, avg=%ld", CPU->id, thread->tid,
-                                    CPU->id, atomic_load(&CPU->nrdy),
-                                    atomic_load(&nrdy) / config.cpu_active);
-#endif
-
-                                thread->stolen = true;
-                                thread->state = Entering;
-
-                                irq_spinlock_unlock(&thread->lock, true);
-                                thread_ready(thread);
-
-                                if (--count == 0)
-                                        goto satisfied;
-
-                                /*
-                                 * We are not satisfied yet, focus on another
-                                 * CPU next time.
-                                 *
-                                 */
-                                acpu_bias++;
-
-                                continue;
-                        } else
-                                irq_spinlock_unlock(&(cpu->rq[rq].lock), true);
-
+                        if (steal_thread_from(cpu, rq) && --count == 0)
+                                goto satisfied;
                 }
         }

kernel/generic/src/proc/thread.c

@@ -259 +259 @@
             ++thread->priority : thread->priority;
 
-        cpu_t *cpu;
-        if (thread->nomigrate || thread->fpu_context_engaged) {
-                /* Cannot ready to another CPU */
-                assert(thread->cpu != NULL);
-                cpu = thread->cpu;
-        } else if (thread->stolen) {
-                /* Ready to the stealing CPU */
-                cpu = CPU;
-        } else if (thread->cpu) {
-                /* Prefer the CPU on which the thread ran last */
-                assert(thread->cpu != NULL);
-                cpu = thread->cpu;
-        } else {
-                cpu = CPU;
-        }
+        /* Prefer the CPU on which the thread ran last */
+        cpu_t *cpu = thread->cpu ? thread->cpu : CPU;
 
         thread->state = Ready;