| To: | Mel Gorman <mgorman@xxxxxxx> |
|---|---|
| Subject: | Re: [PATCH 6/7] mm: vmscan: Throttle reclaim if encountering too many dirty pages under writeback |
| From: | Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> |
| Date: | Thu, 18 Aug 2011 16:54:28 -0700 |
| Cc: | Linux-MM <linux-mm@xxxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, XFS <xfs@xxxxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Johannes Weiner <jweiner@xxxxxxxxxx>, Wu Fengguang <fengguang.wu@xxxxxxxxx>, Jan Kara <jack@xxxxxxx>, Rik van Riel <riel@xxxxxxxxxx>, Minchan Kim <minchan.kim@xxxxxxxxx> |
| In-reply-to: | <1312973240-32576-7-git-send-email-mgorman@xxxxxxx> |
| References: | <1312973240-32576-1-git-send-email-mgorman@xxxxxxx> <1312973240-32576-7-git-send-email-mgorman@xxxxxxx> |
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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