Re: [PATCH 11/18] block: add bdi flag to indicate risk of io queueunderrun

[Peter Zijlstra]

On Sun, 2011-09-04 at 09:53 +0800, Wu Fengguang wrote:
> +++ linux-next/mm/page-writeback.c      2011-08-31 14:40:58.000000000 +0800
> @@ -1067,6 +1067,9 @@ static void balance_dirty_pages(struct a
>                                      nr_dirty, bdi_thresh, bdi_dirty,
>                                      start_time);
>  
> +               if (unlikely(!dirty_exceeded && bdi_async_underrun(bdi)))
> +                       break;
> +
>                 dirty_ratelimit = bdi->dirty_ratelimit;
>                 pos_ratio = bdi_position_ratio(bdi, dirty_thresh,
>                                                background_thresh, nr_dirty,

So dirty_exceeded looks like:


1109                 dirty_exceeded = (bdi_dirty > bdi_thresh) ||
1110                                   (nr_dirty > dirty_thresh);

Would it make sense to write it as:

	if (nr_dirty > dirty_thresh || 
	    (nr_dirty > freerun && bdi_dirty > bdi_thresh))
		dirty_exceeded = 1;

So that we don't actually throttle bdi thingies when we're still in the
freerun area?

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/