On 30/09/14 01:49 PM, Andy Lutomirski wrote: > > I think it might pay to add an explicit vm_op to authorize > duplication, especially for non-cow mappings. IOW this kind of > extension seems quite magical for anything that doesn't have the > normal COW semantics, including for plain old read-only mappings. Adding a vm_ops table to MAP_PRIVATE|MAP_ANONYMOUS mappings has a significant performance impact. I haven't yet narrowed it down, but there's at least one code path a check of `!vma->vm_ops` for the fast path. One is for transparent huge page faults, so the performance impact makes sense. I'll use a simpler implementation for now since the requirements are very narrow / simple.
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