Re: [PATCH 11/12] vmscan: Write out dirty pages in batch

[Rik van Riel]

On 06/14/2010 07:17 AM, Mel Gorman wrote:
> Page reclaim cleans individual pages using a_ops->writepage() because from
> the VM perspective, it is known that pages in a particular zone must be freed
> soon, it considers the target page to be the oldest and it does not want
> to wait while background flushers cleans other pages. From a filesystem
> perspective this is extremely inefficient as it generates a very seeky
> IO pattern leading to the perverse situation where it can take longer to
> clean all dirty pages than it would have otherwise.

Reclaiming clean pages should be fast enough that this should
make little, if any, difference.

> This patch queues all dirty pages at once to maximise the chances that
> the write requests get merged efficiently. It also makes the next patch
> that avoids writeout from direct reclaim more straight-forward.

However, this is a convincing argument :)

> Signed-off-by: Mel Gorman<mel@xxxxxxxxx>

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

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