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