On Sat, Aug 06, 2011 at 10:35:31PM +0800, Andrea Righi wrote: > On Sat, Aug 06, 2011 at 04:44:51PM +0800, Wu Fengguang wrote: > > Add two fields to task_struct. > > > > 1) account dirtied pages in the individual tasks, for accuracy > > 2) per-task balance_dirty_pages() call intervals, for flexibility > > > > The balance_dirty_pages() call interval (ie. nr_dirtied_pause) will > > scale near-sqrt to the safety gap between dirty pages and threshold. > > > > XXX: The main problem of per-task nr_dirtied is, if 10k tasks start > > dirtying pages at exactly the same time, each task will be assigned a > > large initial nr_dirtied_pause, so that the dirty threshold will be > > exceeded long before each task reached its nr_dirtied_pause and hence > > call balance_dirty_pages(). > > > > Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> > > A minor nitpick below. > > Reviewed-by: Andrea Righi <andrea@xxxxxxxxxxxxxxx> Thank you. > > +/* > > * balance_dirty_pages() must be called by processes which are generating dirty > > * data. It looks at the number of dirty pages in the machine and will force > > * the caller to perform writeback if the system is over `vm_dirty_ratio'. > > I think we should also fix the comment of balance_dirty_pages(), now > that it's IO-less for the caller. Maybe something like: > > /* > * balance_dirty_pages() must be called by processes which are generating dirty > * data. It looks at the number of dirty pages in the machine and will force > * the caller to wait once crossing the dirty threshold. If we're over > * `background_thresh' then the writeback threads are woken to perform some > * writeout. > */ Good catch! I'll add this change to the next patch: /* * balance_dirty_pages() must be called by processes which are generating dirty * data. It looks at the number of dirty pages in the machine and will force - * the caller to perform writeback if the system is over `vm_dirty_ratio'. + * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. * If we're over `background_thresh' then the writeback threads are woken to * perform some writeout. */ Thanks, Fengguang -- 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>