On Sun, 2011-09-04 at 09:53 +0800, Wu Fengguang wrote: > /* > + * After a task dirtied this many pages, balance_dirty_pages_ratelimited_nr() > + * will look to see if it needs to start dirty throttling. > + * > + * If dirty_poll_interval is too low, big NUMA machines will call the expensive > + * global_page_state() too often. So scale it near-sqrt to the safety margin > + * (the number of pages we may dirty without exceeding the dirty limits). > + */ > +static unsigned long dirty_poll_interval(unsigned long dirty, > + unsigned long thresh) > +{ > + if (thresh > dirty) > + return 1UL << (ilog2(thresh - dirty) >> 1); > + > + return 1; > +} Where does that sqrt come from? -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html