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

[mel@skynet.ie (Mel Gorman)]

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