On Thu, Feb 24, 2011 at 09:40:39AM +0900, KAMEZAWA Hiroyuki wrote: [..] > > > If we don't consider the swap IO, any other IO > > > operation from our point of view will happen directly from process > > > context (writes in memory + sync reads from the block device). > > > > Why do we need to account for swap IO? Application never asked for swap > > IO. It is kernel's decision to move soem pages to swap to free up some > > memory. What's the point in charging those pages to application group > > and throttle accordingly? > > > > I think swap I/O should be controlled by memcg's dirty_ratio. > But, IIRC, NEC guy had a requirement for this... > > I think some enterprise cusotmer may want to throttle the whole speed of > swapout I/O (not swapin)...so, they may be glad if they can limit throttle > the I/O against a disk partition or all I/O tagged as 'swapio' rather than > some cgroup name. If swap is on a separate disk, then one can control put write throttling rules on systemwide swapout. Though I still don't understand how that can help. > > But I'm afraid slow swapout may consume much dirty_ratio and make things > worse ;) Exactly. So I think focus should be controlling things earlier and stop applications early before they can either write too much data in page cache etc. Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
