Liu, Jiang wrote:
> Hi Stan,
> Currently Intel 5000 series MCH supports two types of power
> saving: putting memory into low power state and shutting down unused
> memory.
> For the first type of power saving by putting memory into low
> power state, it's really based on memory controller thermal protection
> mechanism and works as below. When the entire system is predicted to be
> idle for a relative long time, the driver will trigger hardware thermal
Hi Liu,
I am just curious is there any rough estimate on how much energy LPS
would save
us over some time lets say on 4 CPU system with 8 G of memory when the
system
is idle about 50% of time?
When you say idle do you mean all CPU's do not access any memory? We do
have some activity on idle systems like clock interrupts (100 per sec)
etc. which
will execute code from ISR. Would that be affected?
> protection mechanism to throttle memory access requests which has
> similar effection of frequence deduction. When system is in thermal
> protection state, all memory contents are preserved and system can
> access all memory but with reduced bandwidth and power consumption. When
>
OK this "transition" to LPS is done by hardware.
We can execute code out of RAM. That would allow us to have a driver
which would turned on memory back (via mem controller) to operate at
full speed.
> system wakes up from idle, driver will restore normal memory operation
> mode. The transition time is about several microseconds. This kind of
> memory power saving will operate on the whole memory instead part of
>
Since LPS applies to whole memory probably it would be not that
practical to have
this with NUMA or xVM .
> them and is feature of Intel 5000 series MCH. Future memory controller
> may support this type of power saving by hardware automatically without
> software's assistance.
>
That would be nice!.
> The second type of memory power saving mechanism is shutting
> down unused memory components. All memory contents will get lost after
> shutdown so it needs OS'es help to free up all memory in a specific
> range before shutting down corresponding memory components. To enable
> this type of power saving, there's much more work needed to be done. OS
> needs to monitor memory usage and provide mechanism to free/move memory
> in a specific range, this ability may also be needed by memory hotplug.
>
I agree the above would require changes to memory allocator some of which
already exist on Sparc platforms to support DR. For xVM we would have to
come up with framework allowing Guest OS to free some of its memory to
pass this info to xVM.
It could provide full power management on memory components conforming
to Solaris PM system by adopting this type of memory power saving
> mechanism. It will get more important and useful in NUMA system, some
> nodes with CPU and memory controller may be entirely shut down when
> system is under low pressure.
> To sum up, the first type memory power saving mechanism is much
> more ease to implement and will take effect when entire system is idle.
> The second type memory power saving mechanism could provide us a cpupm
> like "mempm" with full power management capability in current and future
> systems, but with much much more work.
>
It would be interesting to try first scheme to see how it works in
practice.
Stan
>
> Stan Studzinski <mailto:stan.studzinski at sun.com> wrote:
>
>> On Wed, 12 Mar 2008, Liu, Jiang wrote:
>>
>>
>>> / All,
>>>
>> />/ I would like to propose a project to enable FB-DIMM idle power
>> />/ saving on Intel 5000P/5000V/5000Z MCH chipsets.
>> />/ Intel 5000 series MCH chipsets have a thermal protection
>> />/ mechanism which can be used to reduce FB-DIMM power consumption
>> when />/ system is idle. This power saving mechanism has been proven
>> to be very />/ useful in real IDC. On the other hand, platforms based
>> on Intel 5000 />/ series MCH will continue to ship until the end of
>> 2009 plus 4-5 years' />/ lifetime. So enabling FB-DIMM power saving
>> feature can make systems />/ based on 5000 series MCH more power
>> efficient and save money for />/ customers.
>> />/ Any thoughts or suggestions?
>>
>> Hi Gerry,
>>
>> From your proposal it sounds like FB-DIMM power consumption can
>> be reduced when the system is idle.
>> How does this work? From your previous emails this feature applies
>> to whole memory which means that one can not turnoff specified chunks
>> of memory. Is this correct?
>> Does this mean that for memory in a "lower power state" (or LPS) all
>> data is preserved?.
>> From what I understand so far is that if system tries to access LPS
>> memory the software has to enable memory (via register) and then
>> memory can be accessed again.
>>
>> When the system is idle and the memory is off we can't execute code
>> from RAM?
>>
>> Stan
>>
>> />/
>> />/ Liu Jiang (Gerry)
>> />/ Senior Software Engineer
>> />/ OpenSolaris, OTC
>> />/ Tel: (8610)82611515-1643
>> />/ iNet: 8758-1643
>> /
>>
