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On Wed, 4 Feb 2004, Andrew Morton wrote: > > pfn_valid() could become quite expensive indeed, and it lies on super-duper > hotpaths. Yes. However, sometimes it is the only choice. So it does need to be fixed, and if it ends up being a noticeable perofmance problem, then we can look at the hot-paths one by one and see if we can avoid using it. We probably can, most of the time. > An alternative which is less conceptually clean but should work in this > case is to mark all vma's which were created by /dev/mem mappings as VM_IO, > and test that in remap_page_range(). Hmm.. Grepping for "pfn_valid()", I'm starting to suspect that yes, with a VM_IO approach and a fixed virt_addr_valid(), there really aren't any other uses. (virt_addr_valid() is useful for debugging and for validation of untrusted pointers, but pfn_valid() just isn't very good for it. Never really was: it started out as an ugly hack, and it never got cleaned up. It should be easily fixable with something _proper_). Linus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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