Re: [PATCH 7/8] writeback: sync old inodes first in background writeback

From: Rik van Riel
Date: Mon Jul 19 2010 - 14:44:20 EST


On 07/19/2010 09:11 AM, Mel Gorman wrote:
From: Wu Fengguang<fengguang.wu@xxxxxxxxx>

A background flush work may run for ever. So it's reasonable for it to
mimic the kupdate behavior of syncing old/expired inodes first.

This behavior also makes sense from the perspective of page reclaim.
File pages are added to the inactive list and promoted if referenced
after one recycling. If not referenced, it's very easy for pages to be
cleaned from reclaim context which is inefficient in terms of IO. If
background flush is cleaning pages, it's best it cleans old pages to
help minimise IO from reclaim.

Signed-off-by: Wu Fengguang<fengguang.wu@xxxxxxxxx>
Signed-off-by: Mel Gorman<mel@xxxxxxxxx>

Acked-by: Rik van Riel <riel@xxxxxxxxxx>

It can probably be optimized, but we really need something
like this...
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