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    Subject[PATCH 2.5.47] NUMA scheduler (2/2)
    Date
    And here's the second part.

    Erich

    On Monday 11 November 2002 16:13, Erich Focht wrote:
    > here come the NUMA scheduler patches for 2.5.47 which emerged from
    > Michael's and my work on NUMA schedulers. As usual in two parts:
    >
    > 01-numa-sched-core-2.5.47-21.patch: core NUMA scheduler infrastructure
    > providing a node aware load_balancer
    >
    > 02-numa-sched-ilb-2.5.47-21.patch: initial load balancing, selects
    > least loaded node & CPU at exec()
    diff -urN a/fs/exec.c b/fs/exec.c
    --- a/fs/exec.c Mon Nov 11 04:28:10 2002
    +++ b/fs/exec.c Mon Nov 11 14:49:13 2002
    @@ -1022,6 +1022,8 @@
    int retval;
    int i;

    + sched_balance_exec();
    +
    file = open_exec(filename);

    retval = PTR_ERR(file);
    diff -urN a/include/linux/sched.h b/include/linux/sched.h
    --- a/include/linux/sched.h Mon Nov 11 14:44:04 2002
    +++ b/include/linux/sched.h Mon Nov 11 14:49:13 2002
    @@ -159,7 +159,19 @@
    unsigned long system, int cpu);
    extern void scheduler_tick(int user_tick, int system);
    extern unsigned long cache_decay_ticks;
    -
    +#ifdef CONFIG_NUMA
    +extern void sched_balance_exec(void);
    +extern void node_nr_running_init(void);
    +#define nr_running_inc(rq) atomic_inc(rq->node_ptr); \
    + rq->nr_running++
    +#define nr_running_dec(rq) atomic_dec(rq->node_ptr); \
    + rq->nr_running--
    +#else
    +#define sched_balance_exec() {}
    +#define node_nr_running_init() {}
    +#define nr_running_inc(rq) rq->nr_running++
    +#define nr_running_dec(rq) rq->nr_running--
    +#endif

    #define MAX_SCHEDULE_TIMEOUT LONG_MAX
    extern signed long FASTCALL(schedule_timeout(signed long timeout));
    diff -urN a/init/main.c b/init/main.c
    --- a/init/main.c Mon Nov 11 04:28:05 2002
    +++ b/init/main.c Mon Nov 11 14:49:13 2002
    @@ -499,6 +499,7 @@

    migration_init();
    #endif
    + node_nr_running_init();
    spawn_ksoftirqd();
    }

    diff -urN a/kernel/sched.c b/kernel/sched.c
    --- a/kernel/sched.c Mon Nov 11 14:44:04 2002
    +++ b/kernel/sched.c Mon Nov 11 14:49:13 2002
    @@ -153,6 +153,7 @@
    task_t *curr, *idle;
    prio_array_t *active, *expired, arrays[2];
    int prev_nr_running[NR_CPUS];
    + atomic_t * node_ptr;

    task_t *migration_thread;
    struct list_head migration_queue;
    @@ -346,7 +347,7 @@
    p->prio = effective_prio(p);
    }
    enqueue_task(p, array);
    - rq->nr_running++;
    + nr_running_inc(rq);
    }

    /*
    @@ -354,7 +355,7 @@
    */
    static inline void deactivate_task(struct task_struct *p, runqueue_t *rq)
    {
    - rq->nr_running--;
    + nr_running_dec(rq);
    if (p->state == TASK_UNINTERRUPTIBLE)
    rq->nr_uninterruptible++;
    dequeue_task(p, p->array);
    @@ -841,9 +842,9 @@
    static inline void pull_task(runqueue_t *src_rq, prio_array_t *src_array, task_t *p, runqueue_t *this_rq, int this_cpu)
    {
    dequeue_task(p, src_array);
    - src_rq->nr_running--;
    + nr_running_dec(src_rq);
    set_task_cpu(p, this_cpu);
    - this_rq->nr_running++;
    + nr_running_inc(this_rq);
    enqueue_task(p, this_rq->active);
    /*
    * Note that idle threads have a prio of MAX_PRIO, for this test
    @@ -2253,6 +2254,83 @@

    #endif

    +#if CONFIG_NUMA
    +static atomic_t node_nr_running[MAX_NUMNODES] ____cacheline_maxaligned_in_smp = {[0 ...MAX_NUMNODES-1] = ATOMIC_INIT(0)};
    +
    +__init void node_nr_running_init(void)
    +{
    + int i;
    +
    + for (i = 0; i < NR_CPUS; i++) {
    + cpu_rq(i)->node_ptr = &node_nr_running[__cpu_to_node(i)];
    + }
    + return;
    +}
    +
    +/*
    + * If dest_cpu is allowed for this process, migrate the task to it.
    + * This is accomplished by forcing the cpu_allowed mask to only
    + * allow dest_cpu, which will force the cpu onto dest_cpu. Then
    + * the cpu_allowed mask is restored.
    + */
    +static void sched_migrate_task(task_t *p, int dest_cpu)
    +{
    + unsigned long old_mask;
    +
    + old_mask = p->cpus_allowed;
    + if (!(old_mask & (1UL << dest_cpu)))
    + return;
    + /* force the process onto the specified CPU */
    + set_cpus_allowed(p, 1UL << dest_cpu);
    +
    + /* restore the cpus allowed mask */
    + set_cpus_allowed(p, old_mask);
    +}
    +
    +/*
    + * Find the least loaded CPU. Slightly favor the current CPU by
    + * setting its runqueue length as the minimum to start.
    + */
    +static int sched_best_cpu(struct task_struct *p)
    +{
    + int i, minload, load, best_cpu, node = 0;
    +
    + best_cpu = task_cpu(p);
    + if (cpu_rq(best_cpu)->nr_running <= 2)
    + return best_cpu;
    +
    + minload = 10000000;
    + for (i = 0; i < numnodes; i++) {
    + load = atomic_read(&node_nr_running[i]);
    + if (load < minload) {
    + minload = load;
    + node = i;
    + }
    + }
    + minload = 10000000;
    + loop_over_node(i,node) {
    + if (!cpu_online(i))
    + continue;
    + if (cpu_rq(i)->nr_running < minload) {
    + best_cpu = i;
    + minload = cpu_rq(i)->nr_running;
    + }
    + }
    + return best_cpu;
    +}
    +
    +void sched_balance_exec(void)
    +{
    + int new_cpu;
    +
    + if (numnodes > 1) {
    + new_cpu = sched_best_cpu(current);
    + if (new_cpu != smp_processor_id())
    + sched_migrate_task(current, new_cpu);
    + }
    +}
    +#endif /* CONFIG_NUMA */
    +
    #if CONFIG_SMP || CONFIG_PREEMPT
    /*
    * The 'big kernel lock'
    @@ -2314,6 +2392,10 @@
    spin_lock_init(&rq->lock);
    INIT_LIST_HEAD(&rq->migration_queue);
    atomic_set(&rq->nr_iowait, 0);
    +#if CONFIG_NUMA
    + rq->node_ptr = &node_nr_running[0];
    +#endif /* CONFIG_NUMA */
    +

    for (j = 0; j < 2; j++) {
    array = rq->arrays + j;
    \
     
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