On Wed, Mar 17, 2010 at 06:22:29PM +0200, Avi Kivity wrote: > They should be reorderable. Otherwise host filesystems on several > volumes would suffer the same problems. They are reordable, just not as extremly as the the page cache. Remember that the request queue really is just a relatively small queue of outstanding I/O, and that is absolutely intentional. Large scale _caching_ is done by the VM in the pagecache, with all the usual aging, pressure, etc algorithms applied to it. The block devices have a relatively small fixed size request queue associated with it to facilitate request merging and limited reordering and having fully set up I/O requests for the device. -- 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>