Re: [00/17] Large Blocksize Support V3

Christoph Lameter
2007-04-25T15:23:13Z

On Wed, 25 Apr 2007, Mel Gorman wrote:

> HIGHMEM I can understand because I suppose the kmap() issue is still in
> there, but why 32 bit? Is this temporary or do you expect to see it
> fixed up later?

It could be fixed but I only tested with 64 bit. Jens's report shows that
my skepticism was justified. 32 bit has only small memory and suffers from
VM crappiness due to highmem, bouncing due to dma zones etc etc. Its a big
mess that I would like to avoid dealing with for now. Lots of corner cases
that need consideration. When we actually merge this then we can deal with
all the cases. If some cases cannot be dealt with then the large blocksize
support will not be available if another particular feature is
enabled.

> > How well Mel's antifrag/defrag methods address this issue still has to
> > be seen.
> The grouping pages by mobility should hold up for ext2 and XFS because
> their page cache pages are reclaimable/movable and will get grouped with
> other pages that are reclaimable/movable. ramfs may be a problem if it was
> heavily used but lets see how things pan out.

Sounds good.