On Wed, 1 Dec 2010 21:38:18 +0800 Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote: > It shows that > > 1) io_schedule_timeout(200ms) always return immediately for iostat, > forming a busy loop. How can this happen? When iostat received > some signal? Then we may have to break out of the loop on catching > signals. Note that I already have > if (fatal_signal_pending(current)) > break; > in the balance_dirty_pages() loop. Obviously that's not enough. Presumably the calling task has singal_pending(). Using TASK_INTERRUPTIBLE in balance_dirty_pages() seems wrong. If it's going to do that then it must break out if signal_pending(), otherwise it's pretty much guaranteed to degenerate into a busywait loop. Plus we *do* want these processes to appear in D state and to contribute to load average. So it should be TASK_UNINTERRUPTIBLE. -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>