On Mon, Nov 21, 2011 at 06:00:04PM +0800, Christoph Hellwig wrote: > On Mon, Nov 21, 2011 at 05:18:20PM +0800, Wu Fengguang wrote: > > This looks reasonable: smaller device tend to be slower (USB sticks as > > well as micro/mobile/old hard disks). > > > > Given that the non-rotational attribute is not always reported, we can > > take disk size as a max readahead size hint. This patch uses a formula > > that generates the following concrete limits: > > Given that you mentioned the rotational flag and device size in this > mail, as well as benchmarking with an intel SSD - did you measure > how useful large read ahead sizes still are with highend Flash device > that have extremly high read IOP rates? I don't know -- I don't have access to such highend devices. However the patch changelog has the simple test script. It would be high appreciated if someone can help collect the data :) Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>