Re: The performance and behaviour of the anti-fragmentation related patches

Mel Gorman
2007-03-02T17:28:23Z

On (02/03/07 09:19), Christoph Lameter didst pronounce:
> On Fri, 2 Mar 2007, Mel Gorman wrote:
>
> > However, if that is objectionable, I'd at least like to see zone-based patches
> > go into -mm on the expectation that the memory hot-remove patches will be
> > able to use the infrastructure. It's not ideal for hugepages and it is not my
> > first preference, but it's a step in the right direction. Is this reasonable?
>
> I still think that the list based approach is sufficient for memory
> hotplug if one restricts the location of the unmovable MAX_ORDER chunks
> to not overlap the memory area where we would like to be able to remove
> memory.

Yes, true. In the part where I bias placements of unmovable pages at
lower PFNs, additional steps would need to be taken. Specifically, the
lowest block MAX_ORDER_NR_PAGES used for movable pages would need to be
reclaimed for unmovable allocations.

> In very pressing memory situations where we have too much
> unmovable memory we could dynamically disable memory hotplug. There
> would be no need for this partitioning and additional zones.
>

It's simply more complex. I believe it's doable. The main plus going for
the zone is that it is a clearly understood concept and it gives hard
guarantees.

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab