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

Christoph Hellwig
2010-07-19T14:21:47Z

On Mon, Jul 19, 2010 at 02:11:29PM +0100, Mel Gorman wrote:
> From: Wu Fengguang <fengguang.wu@intel.com>
>
> 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.

Yes, we absolutely do this. Wu, do you have an improved version of the
pending or should we put it in this version for now?