On Thu, Feb 24, 2011 at 09:40:39AM +0900, KAMEZAWA Hiroyuki wrote:

[..]

quoted

quoted

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, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  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@kvack.org"> email@kvack.org </a>