On Mon, Jul 26, 2010 at 11:11:37AM +0800, Rik van Riel wrote: > On 07/25/2010 11:08 PM, Wu Fengguang wrote: > > > We do need some throttling under memory pressure. However stall time > > more than 1s is not acceptable. A simple congestion_wait() may be > > better, since it waits on _any_ IO completion (which will likely > > release a set of PG_reclaim pages) rather than one specific IO > > completion. This makes much smoother stall time. > > wait_on_page_writeback() shall really be the last resort. > > DEF_PRIORITY/3 means 1/16=6.25%, which is closer. > > I agree with the max 1 second stall time, but 6.25% of > memory could be an awful lot of pages to scan on a system > with 1TB of memory :) I totally ignored the 1TB systems out of this topic, because in such systems, <PAGE_ALLOC_COSTLY_ORDER pages are easily available? :) > Not sure what the best approach is, just pointing out > that DEF_PRIORITY/3 may be too much for large systems... What if DEF_PRIORITY/3 is used under PAGE_ALLOC_COSTLY_ORDER? Thanks, Fengguang -- 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>