Re: [PATCH 05/10] writeback: per task dirty rate limit

Peter Zijlstra
2011-08-26T12:51:49Z

On Fri, 2011-08-26 at 19:38 +0800, Wu Fengguang wrote:
> + preempt_disable();
> /*
> - * Check the rate limiting. Also, we do not want to throttle real-time
> - * tasks in balance_dirty_pages(). Period.
> + * This prevents one CPU to accumulate too many dirtied pages without
> + * calling into balance_dirty_pages(), which can happen when there are
> + * 1000+ tasks, all of them start dirtying pages at exactly the same
> + * time, hence all honoured too large initial task->nr_dirtied_pause.
> */
> - preempt_disable();
> p = &__get_cpu_var(bdp_ratelimits);

p = &get_cpu_var(bdp_ratelimits);

> - *p += nr_pages_dirtied;
> - if (unlikely(*p >= ratelimit)) {
> - ratelimit = sync_writeback_pages(*p);
> + if (unlikely(current->nr_dirtied >= ratelimit))
> *p = 0;
> - preempt_enable();
> - balance_dirty_pages(mapping, ratelimit);
> - return;
> + else {
> + *p += nr_pages_dirtied;
> + if (unlikely(*p >= ratelimit_pages)) {
> + *p = 0;
> + ratelimit = 0;
> + }
> }
> preempt_enable();

put_cpu_var(bdp_ratelimits);