Messages in this thread | | | Date | Tue, 27 May 2014 19:29:30 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH 0/5] VM_PINNED |
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On Tue, May 27, 2014 at 11:56:44AM -0500, Christoph Lameter wrote: > On Tue, 27 May 2014, Peter Zijlstra wrote: > > > > 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). > > alloc_pages_vma() is used for all paths where we populate address ranges > with pages. This is what we are doing when pinning. Pages are not > allocated outside of a vma context. > > What do you mean by shared pages that are not shmem pages? AnonPages that > are referenced from multiple processes?
Regular files.. they get allocated through __page_cache_alloc(). AFAIK there is nothing stopping people from pinning file pages for RDMA or other purposes. Unusual maybe, but certainly not impossible, and therefore we must be able to handle it.
> > 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? > > Migration is expensive and the memory registration overhead already > causes lots of complaints.
Sure, but first to the simple thing, then if its a problem do something else.
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