Re: [PATCH 3/5] writeback: dirty rate control

From: Peter Zijlstra
Date: Tue Aug 09 2011 - 12:17:05 EST

On Tue, 2011-08-09 at 11:50 -0400, Vivek Goyal wrote:
> So IIUC, bdi->dirty_ratelimit is the dynmically adjusted desired rate
> limit (based on postion ratio, dirty_bw and write_bw). But this seems
> to be overall bdi limit and does not seem to take into account the
> number of tasks doing IO to that bdi (as your comment suggests). So
> it probably will track write_bw as opposed to write_bw/N. What am
> I missing?

I think the per task thing comes from him using the pages_dirtied
argument to balance_dirty_pages() to compute the sleep time. Although
I'm not quite sure how he keeps fairness in light of the sleep time
bounding to MAX_PAUSE.

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