On 2012-12-03 19:53, Jeff Moyer wrote:
> Hi,
>
> In realtime environments, it may be desirable to keep the per-bdi
> flusher threads from running on certain cpus. This patch adds a
> cpu_list file to /sys/class/bdi/* to enable this. The default is to tie
> the flusher threads to the same numa node as the backing device (though
> I could be convinced to make it a mask of all cpus to avoid a change in
> behaviour).
Looks sane, and I think defaulting to the home node is a sane default.
One comment:
> + ret = cpulist_parse(buf, newmask);
> + if (!ret) {
> + spin_lock(&bdi->wb_lock);
> + task = wb->task;
> + if (task)
> + get_task_struct(task);
> + spin_unlock(&bdi->wb_lock);
bdi->wb_lock needs to be bh safe. The above should have caused lockdep
warnings for you.
> + if (task) {
> + ret = set_cpus_allowed_ptr(task, newmask);
> + put_task_struct(task);
> + }
> + if (ret == 0) {
> + mutex_lock(&bdi->flusher_cpumask_mutex);
> + cpumask_copy(bdi->flusher_cpumask, newmask);
> + mutex_unlock(&bdi->flusher_cpumask_mutex);
> + ret = count;
> + }
> + }
> @@ -437,6 +488,14 @@ static int bdi_forker_thread(void *ptr)
> spin_lock_bh(&bdi->wb_lock);
> bdi->wb.task = task;
> spin_unlock_bh(&bdi->wb_lock);
> + mutex_lock(&bdi->flusher_cpumask_mutex);
> + ret = set_cpus_allowed_ptr(task,
> + bdi->flusher_cpumask);
> + mutex_unlock(&bdi->flusher_cpumask_mutex);
It'd be very useful if we had a kthread_create_cpu_on_cpumask() instead
of a _node() variant, since the latter could easily be implemented on
top of the former. But not really a show stopper for the patch...
--
Jens Axboe
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