/proc/sys/vm/mmap_min_addr missing

[Baruch Siach]

Hi Valery,

On Mon, Jan 14, 2013 at 01:40:14PM -0800, Valery Reznic wrote:
> Recently I stumbled upon some mystery that I can't understand.
> My Google search bring no results.
> 
> I have 3 VM with different Linuxes that run under QEMU and now I noticed that
> all of them don't have /proc/sys/vm/mmap_min_addr files (/proc is mounted)
> 
> I am sure that this file was here some time ago.
> I didn't recompile kernel in any of those VMs, don't upgrade QEMU - nothing of the sort.
> 
> But those VMs where started and stopped multiple times.
> 
> So my questions:
> 1. What happened, where this file gone?
> 2. How can I get it back?

The existence of mmap_min_addr depends on the CONFIG_MMU kernel config symbol 
(see kernel/sysctl.c).  Are you by any chance running MMU-less architectures 
under QEMU? If so, there is nothing you can do to get mmap_min_addr back, as 
this is an inherent limitation of MMU-less architectures.

> My host system (Fedora 12, x86-64) has this file.

baruch

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