On 04/18/2013 10:40 PM, Dave Hansen wrote: > On 04/09/2013 02:45 PM, Srivatsa S. Bhat wrote: >> 2. Performance overhead is expected to be low: Since we retain the simplicity >> of the algorithm in the page allocation path, page allocation can >> potentially remain as fast as it would be without memory regions. The >> overhead is pushed to the page-freeing paths which are not that critical. > [...] > I still also want to see some hard numbers on: >> However, memory consumes a significant amount of power, potentially upto >> more than a third of total system power on server systems. Please find below, the reference to the publicly available paper I had in mind, when I made that statement: C. Lefurgy, K. Rajamani, F. Rawson, W. Felter, M. Kistler, and Tom Keller. Energy management for commercial servers. In IEEE Computer, pages 39–48, Dec 2003. Here is a quick link to the paper: researcher.ibm.com/files/us-lefurgy/computer2003.pdf On page 40, the paper shows the power-consumption breakdown for an IBM p670 machine, which shows that as much as 40% of the system energy is consumed by the memory sub-system in a mid-range server. I admit that the paper is a little old (I'll see if I can find anything more recent that is publicly available, or perhaps you can verify the same if you have data-sheets for other platforms handy), but given the trend of increasing memory speeds and increasing memory density/capacity in computer systems, the power-consumption of memory is certainly not going to become insignificant all of a sudden. IOW, the above data supports the point I was trying to make - Memory hardware contributes to a significant portion of the power consumption of a system. And since the hardware is now exposing ways to reduce the power consumption, it would be worthwhile to try and exploit it by doing memory power management. Regards, Srivatsa S. Bhat -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>