Re: [RFC][PATCH 0/5] VM_PINNED

[Peter Zijlstra <peterz@infradead.org>]

On Tue, May 27, 2014 at 11:31:21AM -0500, Christoph Lameter wrote:
> On Tue, 27 May 2014, Peter Zijlstra wrote:
> 
> > On Tue, May 27, 2014 at 10:14:10AM -0500, Christoph Lameter wrote:
> > > On Tue, 27 May 2014, Peter Zijlstra wrote:
> > >
> > > > Well, like with IB, they start out as normal userspace pages, and will
> > > > be from ZONE_MOVABLE.
> > >
> > > Well we could change that now I think. If the VMA has VM_PINNED set
> > > pages then do not allocate from ZONE_MOVABLE.
> >
> > But most allocations sites don't have the vma. We allocate page-cache
> > pages based on its address_space/mapping, not on whatever vma they're
> > mapped into.
> 
> Most allocations by the application for an address range also must
> consider a memory allocation policy which is also bound to a vma and we
> have code for that in mm/mempolicy.c
> 
> Code could be easily added to alloc_pages_vma() to consider the pinned
> status on allocation. Remove GFP_MOVABLE if the vma is pinned.

Yes, but alloc_pages_vma() isn't used for shared pages (with exception
of shmem and hugetlbfs).

So whichever way around we have to do the mm_populate() + eviction hook
+ migration code, and since that equally covers the anon case, why
bother?


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