Messages in this thread | | | Subject | Re: [PATCH 08/13] writeback: quit throttling when bdi dirty pages dropped low | From | Peter Zijlstra <> | Date | Wed, 24 Nov 2010 12:13:53 +0100 |
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On Wed, 2010-11-17 at 12:27 +0800, Wu Fengguang wrote:
> @@ -578,6 +579,25 @@ static void balance_dirty_pages(struct a > bdi_stat(bdi, BDI_WRITEBACK); > } > > + /* > + * bdi_thresh takes time to ramp up from the initial 0, > + * especially for slow devices. > + * > + * It's possible that at the moment dirty throttling starts, > + * bdi_dirty = nr_dirty > + * = (background_thresh + dirty_thresh) / 2 > + * >> bdi_thresh > + * Then the task could be blocked for a dozen second to flush > + * all the exceeded (bdi_dirty - bdi_thresh) pages. So offer a > + * complementary way to break out of the loop when 250ms worth > + * of dirty pages have been cleaned during our pause time. > + */ > + if (nr_dirty < dirty_thresh && > + bdi_prev_dirty - bdi_dirty > > + bdi->write_bandwidth >> (PAGE_CACHE_SHIFT + 2)) > + break; > + bdi_prev_dirty = bdi_dirty; > + > if (bdi_dirty >= bdi_thresh) { > pause = HZ/10; > goto pause;
So we're testing to see if during our pause time (<=100ms) we've written out 250ms worth of pages (given our current bandwidth estimation), right?
(1/4th of bandwidth in bytes/s is bytes per 0.25s)
(and in your recent patches you've changed the bw to pages/s so I take it the PAGE_CACHE_SIZE will be gone from all these sites).
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