Re: [PATCH] 2.6.25-rc3-mm1 - Mempolicy: make dequeue_huge_page_vma() obey MPOL_BIND nodemask

[Lee Schermerhorn <Lee.Schermerhorn@hp.com>]

On Wed, 2008-03-05 at 10:03 -0800, Nishanth Aravamudan wrote:
> On 05.03.2008 [11:06:34 -0500], Lee Schermerhorn wrote:
> > PATCH Mempolicy - make dequeue_huge_page_vma() obey MPOL_BIND nodemask
> > 
> > dequeue_huge_page_vma() is not obeying the MPOL_BIND nodemask
> > with the zonelist rework.  It needs to search only zones in 
> > the mempolicy nodemask for hugepages.
> > 
> > Use for_each_zone_zonelist_nodemask() instead of
> > for_each_zone_zonelist().
> > 
> > Note:  this will bloat mm/hugetlb.o a bit until Mel reworks the
> > inlining of the for_each_zone... macros and helpers.
> > 
> > Added mempolicy helper function mpol_bind_nodemask() to hide
> > the details of mempolicy from hugetlb and to avoid
> > #ifdef CONFIG_NUMA in dequeue_huge_page_vma().
> > 
> > Signed-off-by:  Lee Schermerhorn <lee.schermerhorn@hp.com>
> > 
> >  include/linux/mempolicy.h |   13 +++++++++++++
> >  mm/hugetlb.c              |    4 +++-
> >  2 files changed, 16 insertions(+), 1 deletion(-)
> > 
> > Index: linux-2.6.25-rc3-mm1/mm/hugetlb.c
> > ===================================================================
> > --- linux-2.6.25-rc3-mm1.orig/mm/hugetlb.c	2008-03-05 10:35:12.000000000 -0500
> > +++ linux-2.6.25-rc3-mm1/mm/hugetlb.c	2008-03-05 10:37:09.000000000 -0500
> > @@ -99,8 +99,10 @@ static struct page *dequeue_huge_page_vm
> >  					htlb_alloc_mask, &mpol);
> >  	struct zone *zone;
> >  	struct zoneref *z;
> > +	nodemask_t *nodemask = mpol_bind_nodemask(mpol);
> 
> We get this mpol from huge_zonelist(). Would it perhaps make sense to
> pass the nodemask as a parameter, too, to huge_zonelist(), rather than
> adding mpol_bind_nodemask()? This is the only user of it in-tree.

Nish:

I thought of that.  I didn't go that way because I'd either need to pass
a [pointer to a pointer to] a nodemask in addition to the [pointer to a
pointer to] the mpol, so that I can release the reference on the mpol
after the allocation is finished; or I'd need to copy the nodemask
[which can get pretty big] in the allocation path.  I wanted to avoid
both of those.  I suppose I could be convinced that one or the other of
those options is better than the single use helper function.  What do
you think?

Lee

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