When dd in 512bytes, generic_perform_write() calls balance_dirty_pages_ratelimited() 8 times for the same page, but obviously the page is only dirtied once. Fix it by accounting nr_dirtied at page dirty time. Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> --- mm/page-writeback.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- linux-next.orig/mm/page-writeback.c 2011-08-29 19:14:32.000000000 +0800 +++ linux-next/mm/page-writeback.c 2011-08-29 19:14:36.000000000 +0800 @@ -1267,8 +1267,6 @@ void balance_dirty_pages_ratelimited_nr( if (bdi->dirty_exceeded) ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); - current->nr_dirtied += nr_pages_dirtied; - preempt_disable(); /* * This prevents one CPU to accumulate too many dirtied pages without @@ -1778,6 +1776,7 @@ void account_page_dirtied(struct page *p __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); task_dirty_inc(current); task_io_account_write(PAGE_CACHE_SIZE); + current->nr_dirtied++; } } EXPORT_SYMBOL(account_page_dirtied); -- 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>