Hi, On Wed, Jun 29, 2011 at 10:06:24AM -0700, Dave Hansen wrote: > I was kinda hoping for something a bit simpler than that. I'd boil down > what you were saying to this: > > 1. The kernel must be aware of how the pieces of hardware are > mapped in to the system's physical address space > 2. The kernel must have a mechanism in place to minimize access to > specific pieces of hardware > 3. For destructive power-down operations, the kernel should have a > mechanism in place to ensure that no valuable data is contained > in the memory to be powered down. > 4. The kernel must have a mechanism to maintain utilization statistics pertaining to a piece of hardware, so that it can trigger the hardware to power it off 5. Being able to group these pieces of hardware for purpose of higher savings. > Is that complete? > > On Wed, 2011-06-29 at 18:30 +0530, Ankita Garg wrote: > > 1) Dynamic Power Transition: The memory controller can have the ability > > to automatically transition regions of memory into lower power states > > when they are devoid of references for a pre-defined threshold amount of > > time. Memory contents are preserved in the low power states and accessing > > memory that is at a low power state takes a latency hit. > > > > 2) Dynamic Power Off: If a region is free/unallocated, the software can > > indicate to the controller to completely turn off power to a certain > > region. Memory contents are lost and hence the software has to be > > absolutely sure about the usage statistics of the particular region. This > > is a runtime capability, where the required amount of memory can be > > powered 'ON' to match the workload demands. > > > > 3) Partial Array Self-Refresh (PASR): If a certain regions of memory is > > free/unallocated, the software can indicate to the controller to not > > refresh that region when the system goes to suspend-to-ram state and > > thereby save standby power consumption. > > (3) is simply a subset of (2), but with the additional restriction that > the power off can only occur during a suspend operation. > > Let's say we fully implemented support for (2). What would be missing > to support PASR? > Yes, PASR is a subset of (2) from implementation perspective. -- Regards, Ankita Garg (ankita@xxxxxxxxxx) Linux Technology Center IBM India Systems & Technology Labs, Bangalore, India -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>