Re: [RFC 1/3] mm: mmap make MAP_LOCKED really mlock semantic

[Andrew Morton]

On Tue, 28 Apr 2015 14:11:49 +0200 Michal Hocko <mhocko@xxxxxxx> wrote:

> The man page however says
> "
> MAP_LOCKED (since Linux 2.5.37)
>       Lock the pages of the mapped region into memory in the manner of
>       mlock(2).  This flag is ignored in older kernels.
> "

I'm trying to remember why we implemented MAP_LOCKED in the first
place.  Was it better than mmap+mlock in some fashion?

afaict we had a #define MAP_LOCKED in the header file but it wasn't
implemented, so we went and wired it up.  13 years ago:
https://lkml.org/lkml/2002/9/18/108


Anyway...  the third way of doing this is to use plain old mmap() while
mlockall(MCL_FUTURE) is in force.  Has anyone looked at that, checked
that the behaviour is sane and compared it with the mmap+mlock
behaviour, the MAP_LOCKED behaviour and the manpages?


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/