Re: regression in page writeback

[Peter Zijlstra]

On Tue, 2009-09-22 at 16:05 +0800, Wu Fengguang wrote:
> 
> I'm not sure how this patch stopped the "overshooting" behavior.
> Maybe it managed to not start the background pdflush, or the started
> pdflush thread exited because it found writeback is in progress by
> someone else?
> 
> -               if (bdi_nr_reclaimable) {
> +               if (bdi_nr_reclaimable > bdi_thresh) {

The idea is that we shouldn't move more pages from dirty -> writeback
when there's not actually that much dirty left.

Now, I'm not sure about the > bdi_thresh part, I've suggested to maybe
use bdi_thresh/2 a few times, but it generally didn't seem to make much
of a difference.



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