Messages in this thread Patch in this message | | | From | Rusty Russell <> | Subject | Re: [announce] [patch] ultra-scalable O(1) SMP and UP scheduler | Date | Mon, 07 Jan 2002 13:58:02 +1100 |
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In message <Pine.LNX.4.33.0201040050440.1363-100000@localhost.localdomain> you write: > > now that new-year's parties are over things are getting boring again. For > those who want to see and perhaps even try something more complex, i'm > announcing this patch that is a pretty radical rewrite of the Linux > scheduler for 2.5.2-pre6:
Hi Ingo...
Reading through 2.5.2-C1, couple of comments/questions:
sched.c line 402: /* * Current runqueue is empty, try to find work on * other runqueues. * * We call this with the current runqueue locked, * irqs disabled. */ static void load_balance(runqueue_t *this_rq)
This first comment doesn't seem to be true: it also seems to be called from idle_tick and expire task. Perhaps it'd be nicer too, to split load_balance into "if (is_unbalanced(cpu())) pull_task(cpu())". (I like "pull_" and "push_" nomenclature for the scheduler).
sched.c load_balance() line 435:
if ((load > max_load) && (load < prev_max_load) && (rq_tmp != this_rq)) {
Why are you ignoring a CPU with more than the previous maximum load (prev_max_load is incremented earlier)?
sched.c expire_task line 552:
if (p->array != rq->active) { p->need_resched = 1; return; }
I'm not clear how this can happen??
Finally, I gather you want to change smp_processor_id() to cpu()? That's fine (smp_num_cpus => num_cpus() too please), but it'd be nice to have that as a separate patch, rather than getting stuck with BOTH cpu() and smp_processor_id().
Patch below (untested) corrects SMP_CACHE_BYTES alignment, minor comment, and rebalance tick for HZ < 100 (ie. User Mode Linux).
Rusty. PS. Awesome work. -- Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal working-2.5.2-pre9-mingosched/kernel/sched.c working-2.5.2-pre9-mingoschedfix/kernel/sched.c --- working-2.5.2-pre9-mingosched/kernel/sched.c Mon Jan 7 12:39:10 2002 +++ working-2.5.2-pre9-mingoschedfix/kernel/sched.c Mon Jan 7 13:51:39 2002 @@ -43,14 +43,14 @@ * if there is a RT task active in an SMP system but there is no * RT scheduling activity otherwise. */ -static struct runqueue { +struct runqueue { int cpu; spinlock_t lock; unsigned long nr_running, nr_switches, last_rt_event; task_t *curr, *idle; prio_array_t *active, *expired, arrays[2]; - char __pad [SMP_CACHE_BYTES]; -} runqueues [NR_CPUS] __cacheline_aligned; +} ____cacheline_aligned; +static struct runqueue runqueues[NR_CPUS] __cacheline_aligned; #define this_rq() (runqueues + cpu()) #define task_rq(p) (runqueues + (p)->cpu) @@ -102,7 +102,7 @@ * This is the per-process load estimator. Processes that generate * more load than the system can handle get a priority penalty. * - * The estimator uses a 4-entry load-history ringbuffer which is + * The estimator uses a SLEEP_HIST_SIZE-entry load-history ringbuffer which is * updated whenever a task is moved to/from the runqueue. The load * estimate is also updated from the timer tick to get an accurate * estimation of currently executing tasks as well. @@ -511,7 +511,7 @@ spin_unlock(&busiest->lock); } -#define REBALANCE_TICK (HZ/100) +#define REBALANCE_TICK ((HZ/100) ?: 1) void idle_tick(void) { - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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