Re: regression in page writeback

Peter Zijlstra
2009-09-22T08:08:18Z

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.