Re: [PATCH 00/10] mm: Linux VM Infrastructure to support MemoryPower Management

From: Ankita Garg
Date: Thu Jun 16 2011 - 00:21:03 EST


On Mon, Jun 13, 2011 at 01:47:01PM +0900, KAMEZAWA Hiroyuki wrote:
> On Fri, 27 May 2011 18:01:28 +0530
> Ankita Garg <ankita@xxxxxxxxxx> wrote:
> > Hi,
> >
> I'm sorry if you've answered already.
> Is memory hotplug is too bad and cannot be enhanced for this purpose ?
> I wonder
> - make section-size smaller (IIUC, IBM's system has 16MB section size)
> - add per section statistics
> - add a kind of balloon driver which does software memory offline
> (which means making a contiguous chunk of free pages of section_size
> by page migration) in background with regard to memory usage statistics.
> If system says "need more memory!", balloon driver can online pages.
> can work for your purpose. It can allow you page isolatation and
> controls in 16MB unit. If you need whole rework of memory hotplug, I think
> it's better to rewrite memory hotplug, too.

Interesting idea, but a few issues -

- Correctly predicting memory pressure is difficult and thereby being
able to online the required pages at the right time could be a
- Memory hotplug is a heavy operation, so the overhead involved may be
- Powering off memory is just one of the ways in which memory power could
be saved. The platform can also dynamically transition areas of memory
into a content-preserving lower power state if it is not referenced
for a pre-defined threshold of time. In such a case, we would need a
mechanism to soft offline the pages - i.e, no new allocations to be
directed to that memory

Ankita Garg (ankita@xxxxxxxxxx)
Linux Technology Center
IBM India Systems & Technology Labs,
Bangalore, India
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