Re: mlock() issues

[Michael van Elst <mlelstv%serpens.de@localhost>]

On Wed, Oct 20, 2010 at 10:55:46PM +0100, Sad Clouds wrote:
> On Wed, 20 Oct 2010 20:06:41 +0000 (UTC)
> mlelstv%serpens.de@localhost (Michael van Elst) wrote:
> 
> > The soft rlimit and the UVM limit happen to be the same size,
> > which is one third of the real memory.
> > 
> > uvm_pdaemon.c:
> >    uvmexp.wiredmax = uvmexp.npages / 3;
> > 
> > kern_proc.c:
> >    lim = MIN(VM_MAXUSER_ADDRESS, ctob((rlim_t)uvmexp.free));
> >    ...
> >    limit0.pl_rlimit[RLIMIT_MEMLOCK].rlim_cur = lim / 3;
> 
> OK, if I understand you correctly, there is hardcoded limit on how much
> memory can be locked, it is set to 1/3 of total memory and cannot be
> changed.
> 
> If that's the case, then why supplement soft and hard rlimit with UVM
> limit?


The UVM limit is global to all processes, obviously there should
be such a limit to keep the system provided with unlocked pages.

You could probably make this configurable, but so far nobody had
the need to lock a large part of memory and to adjust that limit.


-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."