Messages in this thread | ![/](/images/icornerl.gif) | | Date | Fri, 4 Apr 2003 16:31:54 -0800 | From | Andrew Morton <> | Subject | Re: objrmap and vmtruncate |
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Andrea Arcangeli <andrea@suse.de> wrote: > > the worst part IMHO is that it screwup the vma making the vma->vm_file > totally wrong for the pages in the vma.
Not sure what you mean here. All pages in the vma are backed by the file at vm_file. It is vm_pgoff which is meaningless.
As for your other concerns: yes, I hear you. I suspect something will have to give. Ingo has a better feel for the problems which this code is solving and hopefully he can comment.
Perhaps it is useful to itemise the prblems which we're trying to solve here:
- ZONE_NORMAL consumption by pte_chains
Solved by objrmap and presumably page clustering.
- ZONE_NORMAL consumption by VMAs
Solved by remap_file_pages. Neither objrmap nor page clustering will help here.
- pte_chain setup and teardown CPU cost.
objrmap does not seem to help. Page clustering might, but is unlikely to be enabled on the machines which actually care about the overhead.
- get_unmapped_area() search complexity.
Solved by remap_file_pages and by as-yet unimplemented algorithmic rework.
- pagefault frequency and TLB invalidation cost.
Solved by MAP_POPULATE, could also be solved by MAP_PREFAULT (but it's not really a demonstrated problem).
Anything else?
So looking at the above, remap_file_pages() actually has pretty good coverage.
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