Re: [PATCH 6/7] mm: vmscan: Throttle reclaim if encountering toomany dirty pages under writeback

From: Andrew Morton
Date: Thu Aug 18 2011 - 19:55:25 EST


On Wed, 10 Aug 2011 11:47:19 +0100
Mel Gorman <mgorman@xxxxxxx> wrote:

> The percentage that must be in writeback depends on the priority. At
> default priority, all of them must be dirty. At DEF_PRIORITY-1, 50%
> of them must be, DEF_PRIORITY-2, 25% etc. i.e. as pressure increases
> the greater the likelihood the process will get throttled to allow
> the flusher threads to make some progress.

It'd be nice if the code comment were to capture this piece of implicit
arithmetic. After all, it's a magic number and magic numbers should
stick out like sore thumbs.

And.. how do we know that the chosen magic numbers were optimal?
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