Re: [PATCH 2/2] Helping prezoring with reduced fragmentation allocation

[Marcelo Tosatti <marcelo.tosatti@cyclades.com>]

Hi Andrew,

What are your thoughts about inclusion of Mel's allocator work on -mm ?

On Wed, Feb 02, 2005 at 12:31:36AM +0000, Mel Gorman wrote:
> On Tue, 1 Feb 2005, Christoph Lameter wrote:
> 
> > On Tue, 1 Feb 2005, Mel Gorman wrote:
> >
> > > > Would it not be better to zero the global 2^MAX_ORDER pages by the scrub
> > > > daemon and have a global zeroed page list? That way you may avoid zeroing
> > > > when splitting pages?
> > > >
> > >
> > > Maybe, but right now when there are no 2^MAX_ORDER pages, the scrub daemon
> > > is going to be doing nothing which is why I think it needs to look at the
> > > free pages of lower orders.
> > >
> > > That is solveable though in one of two ways. One, the scrub daemon can
> > > zero pages from the global list and then add them to the USERZERO pool. It
> > > has the advantage of requiring no more memory and is simple. The second is
> > > to create a second global list. However, I think it only makes sense to
> > > have this as part of the scrub daemon patch (I can write it if thats a
> > > problem) rather than a standalone patch from me.
> >
> > Approach one is fine and I will do an update the remaining prezero patches
> > to do just that.
> 
> There is another problem with approach one. Assuming all 2^MAX_ORDER pages
> have been zeroed and in USERZERO pool and there are no other free pages,
> an allocation for the USERRCLM pool would search all the other pools
> before finding the zerod pages. This could really slow things up but it is
> not a problem approach two suffers from.
> 
> > When will your patches be in Linus tree? ;-)
> >
> 
> Your guess is as good as mine :) . I am fairly sure the allocator is
> somewhere in Andrew's list of patches to look at to consider for inclusion
> into -mm so I suppose it'll get a spin in that tree when he feels it's
> ready.