Re: mlockall(MCL_FUTURE) implies MAP_POPULATE

["Jörn Engel" <joern-BHEL68pLQRGGvPXPguhicg@public.gmane.org>]

On Thu, Dec 17, 2015 at 08:06:21AM +0100, Michael Kerrisk (man-pages) wrote:
> 
> So, I just realized that a recent change to the API, plus its
> associated documentation in the mlock(2) pages actually probably
> lessens the chance of this mistake. The next release of man-pages
> will include documentation of MCL_ONFAULT:
> 
>        MCL_CURRENT Lock  all pages which are currently mapped into the
>                    address space of the process.
> 
>        MCL_FUTURE  Lock all pages which will become  mapped  into  the
>                    address  space of the process in the future.  These
>                    could be, for instance, new  pages  required  by  a
>                    growing heap and stack as well as new memory-mapped
>                    files or shared memory regions.
> 
>        MCL_ONFAULT (since Linux 4.4)
>                    Used  together  with  MCL_CURRENT,  MCL_FUTURE,  or
>                    both.   Mark  all  current  (with  MCL_CURRENT)  or
>                    future (with MCL_FUTURE)  mappings  to  lock  pages
>                    when  they are faulted in.  When used with MCL_CUR‐
>                    RENT, all present pages are locked, but  mlockall()
>                    will  not  fault  in  non-present pages.  When used
>                    with MCL_FUTURE, all future mappings will be marked
>                    to  lock  pages  when they are faulted in, but they
>                    will not be populated by the lock when the  mapping
>                    is  created.   MCL_ONFAULT must be used with either
>                    MCL_CURRENT or MCL_FUTURE or both.
> 
> Do you think that text helps?

Yes.  It seems foolproof for the one fool that is me.

Thank you!

Jörn

--
It does not matter how slowly you go, so long as you do not stop.
-- Confucius
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