Re: Linux 2.6.39-rc3

[Joerg Roedel <joro@8bytes.org>]

On Thu, Apr 14, 2011 at 01:03:37PM +0900, Tejun Heo wrote:
> Hello,
> 
> On Wed, Apr 13, 2011 at 07:33:40PM -0700, Linus Torvalds wrote:
> > On Wednesday, April 13, 2011, Linus Torvalds
> > <torvalds@linux-foundation.org> wrote:
> > > On Wednesday, April 13, 2011, H. Peter Anvin <hpa@zytor.com> wrote:
> > >>
> > >> Yes.  However, even if we *do* revert (and the time is running short on
> > >> not reverting) I would like to understand this particular one, simply
> > >> because I think it may very well be a problem that is manifesting itself
> > >> in other ways on other systems.
> > 
> >  sorry, fingerfart. Anyway, I agree 100%.
> > 
> >  we definitely want to also understand the reason for things not
> > working, even if we do revert..
> 
> There were (and still are) places where memblock callers implemented
> ad-hoc top-down allocation by stepping down start limit until
> allocation succeeds.  Several of them have been removed since top-down
> became the default behavior, so simply reverting the commit is likely
> to cause subtle issues.  Maybe the best approach is introducing
> @topdown parameter and use it selectively for pure memory allocations.

Wouldn't it be better to provide a seperate memblock allocation
function which operates top-down and use this one in the places that
need it? This way it wouldn't break code that relies on bottom-up.

	Joerg