On Mon, Aug 27, 2007 at 05:03:36AM -0700, Arjan van de Ven wrote: > On Mon, 27 Aug 2007 19:21:52 +0800 > > > > Because it does the work in small batches of 10 inodes, when the > > system has <=10 dirty inodes, its behavior will reduce to: > > - do a full sweep *at once* on every 25s > > Which means the disk will flicker once every 25s, not bad :) > > 25 seconds is quite not good already though.... it takes a disk a > second or two of no activity to go into low power mode, every 25 > seconds means you now have at least a 10% constant power cost.... > > I don't know the right answer (well other than "make sure inodes aren't > dirty", which involves fixing apps to not do as much file operations, > as well as relatime) but just "every 25s is no big deal" isn't really > the case ;-(
Yeah, 25s may be too frequent... What I meant is that the old behavior could be "write 1-3 inodes on every 5s" if the inodes are dirtied at random times. Now it becomes "write 10 inodes on every 25s". So it is actually better ;-) It's interesting that we want writeback to be smooth on heavy loads and to be 'bursty' on light loads. Increasing dirty_expire_centisecs and decreasing dirty_writeback_centisecs could help it somehow. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
