Messages in this thread | | | Date | Tue, 7 Oct 2014 11:46:04 +0100 | From | "Dr. David Alan Gilbert" <> | Subject | Re: [PATCH 08/17] mm: madvise MADV_USERFAULT |
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* Kirill A. Shutemov (kirill@shutemov.name) wrote: > On Fri, Oct 03, 2014 at 07:07:58PM +0200, Andrea Arcangeli wrote: > > MADV_USERFAULT is a new madvise flag that will set VM_USERFAULT in the > > vma flags. Whenever VM_USERFAULT is set in an anonymous vma, if > > userland touches a still unmapped virtual address, a sigbus signal is > > sent instead of allocating a new page. The sigbus signal handler will > > then resolve the page fault in userland by calling the > > remap_anon_pages syscall. > > Hm. I wounder if this functionality really fits madvise(2) interface: as > far as I understand it, it provides a way to give a *hint* to kernel which > may or may not trigger an action from kernel side. I don't think an > application will behaive reasonably if kernel ignore the *advise* and will > not send SIGBUS, but allocate memory.
Aren't DONTNEED and DONTDUMP similar cases of madvise operations that are expected to do what they say ?
> I would suggest to consider to use some other interface for the > functionality: a new syscall or, perhaps, mprotect().
Dave
> -- > Kirill A. Shutemov -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
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