A minor fix to this patch. While testing the fio mmap workload, bdi->dirty_ratelimit is observed to be knocked down to 1 and then brought up high in regular intervals. The showed up problem is, it took long delays to bring up bdi->dirty_ratelimit due to the round-down problem of the below task_ratelimit calculation: when dirty_ratelimit=1 and pos_ratio = 1.5, the resulted task_ratelimit will be 1, which fooled stops the logic from increasing dirty_ratelimit as long as pos_ratio < 2. The below change (from round-down to round-up) can nicely fix this problem. Thanks, Fengguang --- --- linux-next.orig/mm/page-writeback.c 2011-09-24 15:52:11.000000000 +0800 +++ linux-next/mm/page-writeback.c 2011-09-24 15:52:11.000000000 +0800 @@ -766,6 +766,7 @@ static void bdi_update_dirty_ratelimit(s */ task_ratelimit = (u64)dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT; + task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ /* * A linear estimation of the "balanced" throttle rate. The theory is, -- 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>