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> -- All rights reversed -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>