Re: [00/17] Large Blocksize Support V3

Christoph Lameter
2007-04-27T12:12:10Z

On Fri, 27 Apr 2007, Nick Piggin wrote:

> For the TLB issue, higher order pagecache doesn't help. If distros
> ship with a 4K page size on powerpc, and use some larger pages in
> the pagecache, some people are still going to get angry because
> they wanted to use 64K pages... But I agree 64K pages is too big
> for most things anyway, and 16 would be better as a default (which
> hopefully x86-64 will get one day).

Powerpc supports multiple pagesizes. Maybe we could make mmap use those
page sizes some day if we had a variable order page cache. Your stands on
the issue means that powerpc will be forever crippled and not be able to
use its full potential.

> Anyway, for io performance, there are alternatives, dispite what
> some people seem to be saying. We can submit larger sglists to the
> device for larger ios, which Jens is looking at (which could help
> all types of workloads, not just those with sequential large file
> IO).

Right this could help but it is not addressing the basic requirement for
devices that need large contiguuos chunks of memory for I/O.