[Ksummit-discuss] [CORE TOPIC] Redesign Memory Management layer and more core subsystem

Rik van Riel riel at redhat.com
Fri Jun 13 22:23:03 UTC 2014

On 06/13/2014 05:36 PM, Benjamin Herrenschmidt wrote:
> On Fri, 2014-06-13 at 12:02 -0500, Christoph Lameter wrote:
>> On Thu, 12 Jun 2014, Phillip Lougher wrote:
>>>> 1. The need to use larger order pages, and the resulting problems with
>>>> fragmentation. Memory sizes grow and therefore the number of page structs
>>>> where state has to be maintained. Maybe there is something different? If
>>>> we use hugepages then we have 511 useless page structs. Some apps need

>> It is solvable if the objects are inherent movable. If any object
>> allocated provides a function that makes an object movable then
>> defragmentation is possible and therefore large contiguous area of memory
>> can be created at any time.
> Another interesting thing is migration of pages with mapped DMA on
> them :-)
> Our IOMMUs support that, but there isn't a way to hook that up into
> Linux page migration that wouldn't suck massively at this point.

The HMM stuff Jerome Glisse is working on may be a suitable
framework to add call callbacks for things like migration to.

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