On Fri, Jun 10, 2011 at 07:08:07PM +0100, Matthew Garrett wrote:

On Fri, Jun 10, 2011 at 10:52:48AM -0700, Paul E. McKenney wrote:

quoted

On Fri, Jun 10, 2011 at 06:23:07PM +0100, Matthew Garrett wrote:

quoted

I haven't seen too many ARM servers with 256GB of RAM :) I'm mostly 
looking at this from an x86 perspective.

But I have seen ARM embedded systems with CPU power consumption in
the milliwatt range, which greatly reduces the amount of RAM required
to get significant power savings from this approach.  Three orders
of magnitude less CPU power consumption translates (roughly) to three
orders of magnitude less memory required -- and embedded devices with
more than 256MB of memory are quite common.

I'm not saying that powering down memory isn't a win, just that in the 
server market we're not even getting unused memory into self refresh at 
the moment. If we can gain that hardware capability then sub-node zoning 
means that we can look at allocating (and migrating?) RAM in such a way 
as to get a lot of the win that we'd gain from actually cutting the 
power, without the added overhead of actually shrinking our working set.

Agreed.

And if I understand you correctly, then the patches that Ankita posted
should help your self-refresh case, along with the originally intended
the power-down case and special-purpose use of memory case.

							Thanx, Paul

--
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>